Forem: Eric The Coder

Python : String Manipulations

Eric The Coder — Sat, 23 Apr 2022 14:48:26 +0000

The Python crash course is free and will be posted here on dev.to. I will publish a new article every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

String Manipulations

Let's now see in a little more detail how to create and manipulate character strings (Strings) with Python.

A variable of type String can be created with single or double quotes

name = 'Mike'

# or

name = "Mike"

Python allows you to insert special characters into your Strings.

message = "Hello \nWorld"
print(message)
# Hello
# World

The special character “\n” will be replaced by a line break. Python provides you with several special characters. Here is a list: https://www.w3schools.com/python/gloss_python_escape_characters.asp

Interpolation

Using the “f” prefix displays the contents of the variable specified between the brackets {}

name = "Mike"

print(f"Hello {name}")
# Hello Mike

Python can also execute any expression inside the {} brackets, so this concept can become very powerful. Here is an example:

name = "Mike"

print(f"Hello {name.upper()}")
# Hello MIKE

It is also possible to join two Strings with the "+" (plus) operator

name = "Mike"

print("Hello " + name)
# Hello Mike

Ignore special characters

Using the “r” prefix displays the contents of the String as is. That is to say without taking into account special characters (ex. \n)

message = r"https:\\example.com\index.html"
print(message)
# https:\\example.com\index.html

Here the use of the “r” prefix allows the path to be displayed correctly. Otherwise Python would have interpreted the double backslash "\\" as a special character.

String over multiple lines

Python also allows you to create a String exactly as entered even with line breaks. To do this you must use three quotes.

message = """This is multiline
String that is easier to
read and assign"""

print(message)
# This is multiline
# String that is easier to
# read and assign

As a result, reading the String in the code is very explicit.

Retrieving part of String

Python allows to retrieve only part of the String.

A String variable is indeed composed of several characters that can be read one by one or in groups. Here is some example

product = "iPhone 12"
# position 012345678

print(product[0]) 
# i

print(product[2]) 
# h

print(product[1:6])
# Phone

Each character is associated with a position number. The first position is always 0. To access a particular position, it must be specified between square brackets []

Note that it is not possible to modify the String in this way. Any attempt to modify will return an error.

product = "iPhone 12"
product[0] = "e"

# TypeError: 'str' object does not support item assignment

It is possible to access the characters of the String from the end.

message = "Hello World";

print(message[-1])
# d

Position -1 represents the last character, -2 the penultimate, and so on.

When retrieving several characters, if one of the two positions is omitted, the retrieval will be from the beginning of the String

message = "Hello World";

print(message[:5])
# Hello

print(message[-5:])
# World

String Manipulations

Python has several functions that allow you to transform the contents of the String. Here are a few :

Uppercase and lowercase conversion

name = 'Mike Taylor'

print(name.lower())
# mike taylor

print(name.upper())
# MIKE TAYLOR

Remove white spaces before and after a String

message = "  Hello World        "

print(message.strip())
# "Hello World"

Return the number of characters in the String

name = "Mike Taylor"

nb_char = len(name)

print(nb_char)
# 11

Change the first letter of a String to uppercase

name = "mike"

name_cap = name.capitalize() 

print(name_cap)
# Mike

Change the first letter of all words in a String to uppercase

name = 'mike Taylor'

name_title = name.title() 

print(name_title)
# Mike Taylor

Check if the String starts or ends with a particular character or characters

name = 'Mike'

print(name.startswith('M')) 
# True

print(name.endswith('ke')) 
# True

Replace part of the String with other characters

name = "Mike"

new_name = name.replace('M', 'P')

print(new_name)
# Pike

Return the position of a specific character

name = "Mike"

print(name.find('k'))
# 2

Note that the first position always starts at zero and if the character is not found, the function will return -1

Conclusion

That's all for today, I'll post a new article every other day or so. To make sure you don't miss anything, you can follow me on twitter: Follow @ EricTheCoder_

Python : Crash Course

Eric The Coder — Sat, 23 Apr 2022 00:53:44 +0000

What will you learn in this course?

This course will teach you basic concepts in Python. All with easy-to-understand terms and examples. Before learning to run, you must know how to walk. Knowing the basics is essential to master a language like Python.

The crash course is free and will be posted here on dev.to. I will publish a new article every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

Why a crash course?

This type of course allows you to learn a maximum of concepts in a minimum of time.
An accelerated course allows the student to maintain a high level of interest and motivation.
The time saved allows the concepts learned to be put into practice more quickly.
At the end of the accelerated course, the student knows enough about the subject to learn on their own the concepts that have not been covered.

Installing Python

To start coding with Python you need to make sure you have an up-to-date version of Python (version 3.10 or +)

From the terminal, type this command to find out the version of Python installed on your machine.

$ python --version

or

$ python3 --version

If you don't have Python or a version earlier than 3.10, you can get the latest version of Python from the official site: https://www.python.org/downloads/

If you want to start coding immediately and install Python later you can use a web-based (free) version of Python.

Here is the link:

https://replit.com/languages/python3

Code Editor

To follow this tutorial you will need to use a code editor. There are several choices, if you don't have a favorite editor yet, I recommend Microsoft's vscode.

Here is the link:

https://code.visualstudio.com/download

In this tutorial we will not teach how vscode works. If you want to learn the basics of vscode, there are several free tools available.

One option I recommend is to configure vscode to allow running from the terminal. Here is a link on the instructions for doing this:

Max OSX

https://code.visualstudio.com/docs/setup/mac

Windows

https://code.visualstudio.com/docs/setup/windows

Run python code

Once the installation of Python is complete on your machine, it is now time to run your first Python code.

In the next sections we will learn together the basics of Python languages. I will therefore invite you to create a folder and a file in order to place the code which will be given as an example.

Create a folder named “demo_python”

~$ mkdir demo_python
~$ cd demo_python

Inside the folder create a file named “main.py”

~$ code main.py

Your first line of code

Add this code in the “main.py” file

print("Hello World")

Here the “print()” instruction is used to display text in the terminal

Once the file is saved, from the terminal you can run it using Python.

~$ python3 main.py

or

~$ python main.py

Python will execute all the lines of code present in the file and display the result in the terminal.

Hello World

Run Python Code Quickly

If you want to run Python code quickly and without creating a file, you can use the shell. The shell is an application that allows you to enter a line of Python code, execute it and display the result immediately.

To run the shell just run Python without adding any argument

~$ python3

or 

~$ python

The command will launch the shell from the terminal

Python 3.9.9 (main, Nov 21 2021, 03:16:13) 
[Clang 13.0.0 (clang-1300.0.29.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> _

Once the application is launched, it is possible to enter a command line after the following characters >>>

Example:

>>> print("Hello World")

Once the command has been entered, press the “return” key and the code will be executed

>>> print("Hello World")
Hello World
>>> _

You will have understood that the shell is more useful for testing a Python command than for writing a real application.

If you are developing a real python application the approach to use is to put the code in files with the extension “.py”

Your first steps with Python

For the next examples, I invite you to use the “main.py” file that we created in the previous example.

The variables

Variables allow you to store information that can be used later by your application.

To define a variable, all you have to do is give it a name and a value.

For example, suppose you want to store the username, you can use a variable and give it the name: name and set its contents equal to “Mike Taylor”

name = "Mike Taylor"
print(name)

Here the variable is called “name” and contains the text “Mike Taylor”. The quotes tell Python that its content is text.

Types of variables

A variable can contain several types of data. In the last example it is text but we could have assigned an integer to it.

num = 25

Note that to be recognized as a number, you must not use quotes ““

With Python, it is not necessary to specify the type of the variable. Python will detect the type automatically depending on the content you assign to it.

Depending on the type detected by Python, it will be possible to perform operations on this variable.

Here is an example :

value = "100"

value2 = 100

Here “value” is a text type variable (string) which contains the text “100”. This variable is not a number that can be used in a mathematical operation.

“value2” is an integer type variable that has the number 100 as its content. This variable is a number and therefore can be used for mathematical operations.

result = value + value
# "100100"

result2 = value2 + value2
# 200

The addition of these two variables does not give the same result. In Python Adding a text variable (string) will pair the two texts together. While the addition of integer variables will mathematically add the two values.

Here are different types of variables that can be defined with Python. We will come back to each of them in detail later.

name = 'Mike' # string (texte)
age = 42 # integer (nombre entier)
price = 199.99 # float (nombre décimal)
is_active = True # boolean (vrai ou faux)

colors = ['red', 'green', 'blue'] # liste
states = ('inactive', 'active', 'archive') # tuple
products = { 'name': 'iPad Pro', 'price': 199.99 } # dictionnaire

In order to simplify the tutorial, from this point, the types of variables will be called by their English name. For example I will not use the term “text” or “integer” but rather “string” and “integer”.

Reporting convention

By convention, Python variables are defined in lowercase letters and may contain the _ character as a separator.

first_name = "Mike"

Comments

It is possible to insert a comment in your code. To do this, you must use the “#” character. Anything after this character will not be executed by Python

# Ceci est un commentaire
name = "Mike Taylor"

age = 27  # Ceci est un commentaire

It is also possible to create multi-line comments with the use of three quotes “”” comments “””

def say_hello():
    """ Cette fonction permet d'afficher un
    messsage de bienvenu sur plusieurs lignes """ 

   print("Hello World")

Conclusion

That's all for today, I'll post a new article every other day or so. To make sure you don't miss anything, you can follow me on twitter: Follow @ EricTheCoder_

PHP crash course : require, include, files manipulation and enumerations

Eric The Coder — Fri, 28 Jan 2022 15:07:05 +0000

Today you will learn conditionals, loops and functions création in PHP.

This PHP crash course is free and will be posted here on dev.to. I'll be releasing a new article/post every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

require and include

So far we have created only one PHP file for all our tests.

When creating an application it will almost always be otherwise. Very quickly we will need to split/organize our code into multiple files.

Here we will see two instructions that allow you to execute code that has been defined in another file.

To do this we will create two files. The first named message.php and write the following code

<?php

function sendMessage(string $message)
{
    echo $message . '<br>';
}

Here it is simple code from simple. A small function that displays a message and a line break.

Then, create the second file named index.php and write the following code

<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <?php
        require 'message.php';
        sendMessage('Hello World');
    ?>
</body>

</html>

In this example, we discover the require instruction. It allows to include the code of the message.php file. So therefore allows the use of the function sendMessage()

What happens if the file specified as a parameter does not exist? In this case, PHP will return an error.

The include instruction

Allows you to do exactly the same thing as the require instruction except that PHP will not return an error (only a Warning) if the file to include is not present.

require_once et include_once

These instructions are identical to their sister function (require and include). The difference is that PHP will include the file only if it hasn't already.

Manipulation of files and folders

PHP includes several functions to manipulate folders and files on the server

Here are some very useful functions

Create file

file_put_contents("test.txt", "Hello World!");

This function will create the test.txt file (in the current folder) with the content 'Hello World'.

It is possible to specify the folder.

file_put_contents("data/test.txt", "Hello World!");

If the folder does not exist, PHP will return a warning

You can create the folder with mkdir function

mkdir('data');

file_put_contents("data/test.txt", "Hello World!");

Note that to delete a folder you can use the rmdir() function. The folder must be empty for its deletion to be possible.

If you want to create the file in a folder that is parent to the current folder use the colon . .

file_put_contents("../test.txt", "Hello World!");

The file will be created in the parent folder

If the file already exists, the file_put_contents function will replace the existing file. If your goal is to append to the existing file, use the FILE_APPEND option

file_put_contents("test.txt", "Hello World!", FILE_APPEND);

Read a file

$content = file_get_contents("test.txt");

If the file does not exist, PHP will return a warning

To check if the file exists you can use the file_exists() function

if (file_exists('/posts/first.txt')) {
  // do some stuff
}

Read a file line by line

The previous function allowed to read a file at once. There is a function to read line by line.

$file = fopen("test.txt", "r");

while(! feof($file)) {
  $line = fgets($file);
  echo $line. "<br>";
}
fclose($file);

here the file is opened with the 'r' option for read.

The code block will run until the end of file is detected feof()

Write to file line by line

$file = fopen('export.csv', 'w');

Here the file is opened with the 'w' option to create or overwrite. If we wanted to make an addition we could have used the option 'a' to add

Once the file is open, you can insert lines

$array = [
    ['name' => 'Mike', 'age' => 45],
    ['name' => 'John', 'age' => 38],
]

//Write key name as csv header
fputcsv($file, array_keys($array[0]));

//Write lines (format as csv)
foreach ($array as $row) {
    fputcsv($file, $row); 
}
fclose($file);

The fputfile() function allows to write lines. Here we have rather used its sister function fputcsv() which does essentially the same thing but in csv format.

Note that we used an fputcsv before the loop. This line will be the first line of the file and should include the column names. The array_keys() function allows you to retrieve the name of the array keys (name and age)

Enumerations

Enumerations, or "Enums" make it possible to define a personalized “type” which will be limited to one of the possible values among those specified. Enums are a type of object and therefore can be used anywhere an object can be used.

Here is an example statement

// Définir le nom et les valeurs posssible
enum InvoiceStatus
{
    case Sent;
    case Paid;
    case Cancelled;
}

This declaration creates an InvoiceStatus type which can have only three values

InvoiceStatus::Sent

InvoiceStatus::Paid

InvoiceStatus::Cancel

It is possible to use this type in a function with type hint

function printInvoiceStatus(InvoiceStatus $status)
{
    print($status->name);
}

printInvoiceStatus(InvoiceStatus::Sent);
// Sent

The name property is used to retrieve the name of the case

It is possible to associate a value for each of the “case”. To do this, it is absolutely necessary to specify the type of the enum when declaring it: ex. enum InvoiceStatus : int

It is also possible to add a method to our enum

enum InvoiceStatus : int
{
    case Sent = 0;
    case Paid = 1;
    case Cancelled = 2;
}

print(InvoiceStatus::Paid->value);

The value property allows you to retrieve the value associated with the “case”

Just like an object, it is possible to add a method to the Enum

enum InvoiceStatus : int
{
    case Sent = 0;
    case Paid = 1;
    case Cancelled = 2;

    public function text() : string
    {
        return match ($this) {
            self::Sent => 'Sent',
            self::Paid => 'Paid',
            self::Cancelled => 'Cancelled'
        };
    }
}

function getInvoiceStatus(InvoiceStatus $status)
{
    print($status->text());
    print($status->value);
}

getInvoiceStatus(InvoiceStatus::Paid);
// Paid1

The method can access the “case” of the enum via the keyword self::

Finally, each value can call the ex function. InvoiceStatus→text()

Conclusion

That's it for today, I'll be releasing a new article every two days or so. To be sure not to miss anything you can follow me on twitter: Follow @EricTheCoder_

PHP crash course : Conditionals, Loops and Functions

Eric The Coder — Sun, 23 Jan 2022 18:02:50 +0000

Today you will learn conditionals, loops and functions création in PHP.

This PHP crash course is free and will be posted here on dev.to. I'll be releasing a new article/post every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

Conditional execution

In PHP, it is possible to execute a line of code only if a condition is true

if ($name === 'Mike') {
    echo 'Hello Mike';
}

The code enclosed in the parentheses is called an expression. PHP will execute this code and return its boolean value (true or false).

If the result is 'true' then the code contained between the { } will be executed.

If the result is false, nothing will be executed in this if block

Here is another example with the operator greater than « > »

$amount = 120;

if ($amount > 100) {
    echo 'Free shipping';
}

Here the expression ($amount) will return true, so shipping will be free.

It is possible to execute code if the condition is false

$amount = 120;

if ($amount > 100) {
    echo 'Free shipping';
} else {
    echo 'Shipping 9.95$';
}

Here the keyword else executes the code if the expression is 'false'

Finally, it is possible to have several conditions

$amount = 120;

if ($amount > 100) {
    echo 'Free shipping';
} elseif ($amount > 50) {
    echo 'Shipping 9.95$';
} else {
    echo 'Shipping 19.95$';
}

The elseif keyword is used to test another condition. Note that this condition will be tested only if the first condition is false.

If both the first and the second condition are false, then the code in the else section will be executed.

Comparison operator

Here are the different operators that can be used in expressions.

== equal no type check
=== equal with type check
!= not equal
|| or
&& and
> greater than
< less than

it is possible to test several expressions at the same time with the operator &&

if ($amount > 0 && $amount < 50) {
   echo 'The price is between 1 and 49';
}

The same principle applies for the operator or ||

if ($amount === 100 || $amount === 200) {
   echo 'The price is 100$ or 200$';
}

Expressions without a comparison operator

$amount = 0;

if ($amount) {
    echo 'The price is not zéro';
}

Here the expression ($amount) does not contain a comparison operator, despite this fact, this code is valid. Why ? In PHP each expression is converted into a Boolean value. So here 0 is converted to false. Any other value other than zero (or null) would convert to true.

Conversion to boolean value

Here is the list of values that will be converted to false

false

0.0

null

‘0’ (string equal to zero)

‘ ’ (empty string)

All other values will convert to true

Here are some examples of conversion to boolean value

$messsage = 'Hello World'

if ($message) { // true
   echo $messsage;
}

if ($value) {
    echo 'Variable is set';
} else {
    echo 'Variable is unset';
}

Using IF statement in an HTML file

<html lang="en">

<body>
    <?php $isAdmin = true; ?>

    <h1>Home page</h1>

    <?php if ($isAdmin) : ?>
        <p>Welcome Administrator</p>
    <?php else : ?>
        <p>Welcome Guest</p>
    <?php endif ?>

</body>

</html>

Each block of PHP code has an opening and closing tag. The particularity here is the “if” and “else” code block. There's no { }. You can use “:” instead.

Switch

If we have several conditions, the if, elseif ect. can result in hard-to-read code. In this case, the Switch statement helps to simplify your code.

switch ($color) {
    case 'red':
        echo 'Danger';
         break;
    case 'yellow':
        echo 'Warning';
        break;
    case 'green':
        echo 'Success';
        break;
    default:
        echo 'The color is unknown';
}

The first line represents the expression we want to evaluate: switch($color)

Then just include the possible “cases”.

The “break” function prevents the execution from continuing

The “case” default is used if there is no matching case.

Match

New in PHP 8.1, this instruction allows you to return an expression according to a key ⇒ value correspondence

$type = match($color) {
    'red' => 'danger',
    'yellow', 'orange' => 'warning',
    'green' => 'success',
    default => 'Unknown'
};

The first line represents the expression we want to match: match($color)

On the second line we notice that it is possible to match more than one expression at a time.

Then follows a list of key ⇒ value. If no key→value is found, the default key will be executed.

Note that the key can be an expression and the value can also be an expression and even a function

$type = match($color) {
    userID == 100 => openAdmin(),
    userID < 100 && userID > 0 => openUser(),
    default => openOther()
};

Switch ou Match ?

Match is visually simpler but Switch allows to execute more than one line of code for each “box”. Match returns a value which Switch does not. In short, I use Match if possible because I find the instruction more visually refined but otherwise I have no problem with the Switch instruction

Ternary operator ?:

This is a shorthand syntax for an if...else.

Here is an example with if...else

if ($isValid) {
    echo 'user valid';
} else {
    echo 'user not valid';
}

Here is the same example but with the Ternary operator

echo $isValid ? 'user valid' : 'user not valid';

If the expression preceding the operator “?” is true then the value following “?” will be used, otherwise the value following the “:” will be used.

The null coalescing operator ??

The Null coalescing operator returns its first operand if it exists and is not NULL; otherwise it returns its second operand

echo $name ?? 'Mike';  //output 'Mike' if $name is null

Assignment with Null coalescing operator ??

$name ??= 'Mike';

Assigns the value 'Mike' if the variable $name is null

Null safe operator

echo $user?->profile?->activate();

If one of the variables preceding the “?” is null then the value of of the expression will be null

Loops

The “while” loop

Allows a block of code to be executed a certain number of times. The number of times will depend on the conditions. As long as the condition is true, the code block will run.

$number = 1;
while ($number < 10) {
    echo 'value : ' . $number ;
    $number += 1;
}

Here the code block will be executed 9 times.

“do while” loop

Essentially the same principle as the “while” loop, but in this case the block of code will always execute at least once. The condition being tested only at the end of the code block.

$number = 1;
do {
    echo 'value : ' . $number ;
    $number += 1;
} while ($number < 10);

The “for” loop

Used to execute a block of code a number of times defined by a condition.

for ($i = 0; $i < 20; $i++) {
    echo "i value = " . i;
}

The parameter is divided into three sections, the first being the definition of the counter ($i = 0). Then the condition to respect to execute the block of code ($i < 20) and finally the code to execute at each iteration ($i++)

The “foreach” loop

The foreach function executes a block of code for each element of an array.

$names = ['Mike', 'Shawn', 'John'];

foreach($names as $name) { 
   echo 'Hello ' . $name;
}

The first parameter is the name of the array to browse, the second parameter represents the reference to the current element.

Break and Continue

The break and continue statements are used to modify the loop

for ($i = 0; $i < 20; $i++) {
    if ($i % 2 === 0) {
        continue;
    }
    echo $i . '<br>';
}

This loop will print the value of $i, only when the value is odd.

If the value is even ($i % 2 === 0). So we ask the loop to do a continue with the next value.

It is possible to exit the loop at any time with the break instruction

$i = 0;

while ($i < 10000) {
    $i++;
    if ($i == 10) {
        break;
    }
    echo $i . '<br>';
}

Here the loop will stop when $i will have 10 as value

Functions

In PHP there are several functions already pre-defined. It is also possible to create our own functions.

Functions allow us to avoid repeating our code several times. They also allow us to divide our application into small pieces that are easier to maintain.

The syntax for creating a function is quite simple

function hello() {
    echo 'Hello World';
}

Here we use the keyword “function” followed by the name of our function.

Once our function has been created, it is possible to launch its execution

hello();

It is possible to include one or more parameters to our function

function hello($firstName, $lastName) {
    echo 'Hello' . $firstName . ' ' . $lastName;
}

The launch of the function must include the parameters in the order they were declared

hello('Mike', 'Taylor');

A default value can be assigned to a parameter which suddenly makes this parameter optional when calling the function.

function hello($firstName, $lastName = 'none') {
    echo 'Hello' . $firstName . ' ' . $lastName;
}

hello('Mike');
// Mike none

Note that parameters with a default value must absolutely be defined last.

Since version 8 of PHP it is possible to launch a function by naming the parameters. The call is clearer and the order of the parameters does not have to be respected.

hello(lastName: 'Taylor', firstName: 'Mike');

Return

Returns a value when calling the function.

function fullName($firstName, $lastName) {
    return $firstName . ' ' . $lastName;
}

echo fullName('John', 'Doe');

Here the function returns a concatenated string with first name and last name

The echo function will display on the web page the value returned by the fullName() function

Anonymous functions (closure)

Allows the creation of functions without specifying their name. Here is an example :

$sum = function ($a, $b) (
    return $a + $b;
);

echo $sum(10, 15);

Anonymous functions end with a semicolon; And they can't access the parent context variables.

It is possible to pass a variable from the parent context with the statement use

$x = 10;

$sum = function ($a, $b) use $x (
    return $x + $a + $b;
);

echo $sum(10, 15);
// 35

Callback functions

Callback functions are anonymous functions passed as parameters. here is an example

$products = ['iPhone 12', 'iPhone 13', 'iPad', 'iWatch'];

$filtered_products = array_filter($products, function ($product) {
    return str_contains($product, 'Phone');
});

print_r($filtered_products);
// Array ( [0] => iPhone 12 [1] => iPhone 13 )

Here the array_filter() function has an anonymous function as second parameter.

Arrow functions

Allows the use of a shortcut syntax:

$products = ['iPhone 12', 'iPhone 13', 'iPad', 'iWatch'];

$filtered_products = array_filter($products, fn ($product) => str_contains($product, 'Phone'));

print_r($filtered_products);

Note that for the moment, the Arrow functions allow the execution of only one expression. Arrow functions are executed in the current context so they can use variables without having to use the use statement.

Function Type Hint

Note that functions can be typed (string, int, etc.). It is possible to define a type for each of the parameters and a type for the return value of the function

function display(string $first, string $last) : string {
    return "$first $last";
}

Here the $first and $last parameters must be of type string as well as the return value.

There are several other things to know about typed functions, we will come back to this later.

Strict Type

Here is an example of a function with type

function add(int $a, int $b): int
{
    return $a + $b;
}

echo add('10', 20);
// 30

In this example the parameter $a is of type integer. However PHP does not return an error. The reason is that PHP will try to convert the string '10' to an integer. If the conversion is possible then no error is reported.

There are times when you would like PHP to not allow this conversion and only execute if the parameter is really of the specified type. To do this you must add an instruction at the beginning of your file.

declare(strict_types=1);

function add(int $a, int $b): int
{
    return $a + $b;
}

echo add('10', 20);
// TypeError

Here an error is returned because the type of the parameter is not an integer

Conclusion

That's it for today, I'll be releasing a new article every two days or so. To be sure not to miss anything you can follow me on twitter: Follow @EricTheCoder_

PHP crash course : Array manipulation

Eric The Coder — Mon, 17 Jan 2022 13:42:59 +0000

Today you will learn array création and manipulation in PHP.

This PHP crash course is free and will be posted here on dev.to. I'll be releasing a new article/post every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

First, here is a very common scenario in web development that will help you to understand why we need Array.

In the next exemple, we need to display a list of products and their prices.

$product1 = "iPad";
$product2 = "iPhone";
$product3 = "iWatch";

$price1 = 599;
$price2 = 899;
$price3 = 699;

echo $product1 . ' : ' . $price1 . '<br>';
echo $product2 . ' : ' . $price2 . '<br>';
echo $product3 . ' : ' . $price3 . '<br>';

As you can imagine, this code is far from optimal. Imagine if we had 100 products or even 10,000 products.

There is a way to do the previous exemple in a much more efficient way... Arrays.

Arrays in PHP are a lists of values. Values in an array can be of different type.

To define an array we use square brackets [ ]

$products = [];

The variable $products is an array

It is possible to create an array with content

$products = ['iPad', 'iPhone', 'iWatch'];

This array contains three strings: iPad, iPhone, iWatch

Each array element is separated by a comma.

It is possible to have arrays with different type of variable

$array = ['First entry', 100, true];

It is even possible to create an array within an array

$array = ['First entry', 100, ['iPad', 'iPhone'], false];

To access an item

echo $array[0];
// First entry

The elements of an array are indexed from 0. So the first item is at position 0, the second at position 1, and so on.

$array = ['First entry', 100, ['iPad', 'iPhone'], false];
                 0         1           2            3

To access an array within an array you use the following syntax

echo $array[2][1];
// iPhone

Here we display element 2, i.e. ['iPad', 'iPhone']
Then element 1 is iPhone

If you attempt to access a non-existent item. PHP will return a warning and the value null.

$array = ['First entry', 100, true];

echo $array[3];
// null 
// Warning: Undefined array key 3

Count

To determine the number of items in an array you can use the count() function

$array = ['First entry', 100, true];

echo count($array);
// 3

Array manipulation

Add an element at the end of the array

$array[] = 'Last';

// ['First entry', 100, ['iPad', 'iPhone'], false, 'Last']

Remove an element from the array

unset($array[0]);

// [100, ['iPad', 'iPhone'], false, 'Last']

Convert an array to a string with the implode function

$array = ['One', 'Two', 'Three'];
echo implode(', ', $array);
// "One, Two, Three"

The first parameter is the separator.

Transform a string into an array with the explode function

$text = 'Mike, Shawn, John';
echo explode(',', $text); // ['Mike', 'Shawn', 'John'];

The first parameter is the separator.

Iterate through all elements of an array

The foreach function executes code for each element of the array.

$names = ['Mike', 'Shawn', 'John'];

foreach($names as $name) { 
   echo 'Hello ' . $name;
}

The first parameter is the name of the array to browse, the second parameter represents the reference to the current element.

Associative arrays

So far we have learned how arrays work. They have a number key starting from 0.

It is possible to create arrays with a custom key. This is what PHP calls associative arrays.

$person = ['age' => 45, 'genre' => 'men'];

Here 'age' and 'gender' are the keys. 45 and men are the values associated with these keys.
Note that some programming languages call this type of array a dictionary.
Associative arrays are very practical and you must understand them well because you will use them very often. They are perfect for storing information.

$product = ['id' => 100, 'name' => 'iPad', 'price' => 699];

Access to an array value is done with the key

echo "Product :" . $product['name'];

Adding a key/value to the array is possible by specifying a new key

$product['qty'] = 5;

It is possible to check if a key exists

$product = ['id' => 100, 'name' => 'iPad', 'price' => 699];

echo array_key_exists('id', $product);
// true

Loop in an associative array with values and keys

foreach($names as $key => $value) {
   echo $key . ' : ' . $value;
}

Concatenation: Join two arrays

$names1 = ['Mike', 'Paul', 'Tom'];
$names2 = ['John', 'Sam'];

$allNames = array_merge($names1, $names2);
// ['Mike', 'Paul', 'Tom', 'John', 'Sam'];

Concatenation with the spread operator (...)

$names1 = ['Mike', 'Paul', 'Tom'];
$names2 = ['John', 'Sam'];

$allNames = [...$names1, ...$names2];
// ['Mike', 'Paul', 'Tom', 'John', 'Sam'];

Here, the spread operator before the array name (...$names) deconstructs the array.

An array of associative arrays

A pattern that you will use often is an array containing associative arrays.

$items = [
    ['id' => '100', 'name' => 'product 1'],
    ['id' => '200', 'name' => 'product 2'],
    ['id' => '300', 'name' => 'product 3'],
    ['id' => '400', 'name' => 'product 4'],
];

This kind of table is excellent for representing data.
It is possible to loop and display each item

foreach($items as $item) {
    echo $item['name'] . <br>;
}

The 'as' statement create a reference to the array item.

Retrieve part of an array

There are several functions that allow you to retrieve part of an array.
Retrieve only keys or values

$person = ['age' => 45, 'genre' => 'men'];

// Return an array with only keys
echo array_keys($person); // ['age', 'genre']

// Return an array with only values
echo array_values($person); // [45, 'men']

Retrieval of items that match a specific criterion with the array_filter() function

$items = [
    ['id' => 100, 'name' => 'product 1'],
    ['id' => 200, 'name' => 'product 2'],
    ['id' => 300, 'name' => 'product 3'],
    ['id' => 400, 'name' => 'product 4'],
];

$filteredItem = array_filter($items, function ($product) {
    return $product['id'] > 200;
});

print_r($filteredItem);
// $items = [
//    ['id' => '300', 'name' => 'product 3'],
//    ['id' => '400', 'name' => 'product 4'],
// ];

The array_filter() function is a function with a callback function as parameter. For each item in the array an expression will be evaluated. If the expression is true, the current item will be included in the resulting array.

Search in an array

$items = [
  ['id' => '100', 'name' => 'product 1'],
  ['id' => '200', 'name' => 'product 2'],
  ['id' => '300', 'name' => 'product 3'],
  ['id' => '400', 'name' => 'product 4'],
];

$found_key = array_search('product 3', array_column($items, 'name'));
// 2

The array_search() function allows you to search for a specific key according to a search criterion. In the last example we look for the key of 'product 3' in the 'name' column

Create a new array with the array_map() function

$items = [
    ['id' => 100, 'name' => 'product 1'],
    ['id' => 200, 'name' => 'product 2'],
    ['id' => 300, 'name' => 'product 3'],
    ['id' => 400, 'name' => 'product 4'],
];

$mapItems = array_map(function ($product) {
    return [
        'id' => $product['id'] * 2, 
        'name' => $product['name']
    ];
}, $items);

print_r($mapItems);
//[
    ['id' => 200, 'name' => 'product 1'],
    ['id' => 400, 'name' => 'product 2'],
    ['id' => 600, 'name' => 'product 3'],
    ['id' => 800, 'name' => 'product 4'],
];

The array_map() function returns an array that contains what each callback item will return.

The array_map() function must have two parameters: a callback function and an array. ex. array_map(callback function, arrays)

The array_map() function loops over each array item and at the same time builds a new array. Each item in the new array is the result (return) of the callback function. In the last example, each loop returned an item with the id * 2 and the product name.

The original table is not modified, a new table is created.

The array_reduce() function

This function takes an array and reduces it to a single value. Eg returned the result of adding all numbers contains in an array.

$numbers = [2, 4, 6, 100];

$sum = array_reduce($numbers, function ($num, $total) {
    return $total + $num;
}, 0);

print_r($sum);
// 112

The array_reduce() function take two parameters: reference to actual item and a total variable. For each iteration, the callback function return the result in the total variable.

Conclusion

That's it for today, I'll be releasing a new article every two days or so. To be sure not to miss anything you can follow me on twitter: Follow @EricTheCoder_

PHP crash course : Strings and Numbers

Eric The Coder — Fri, 14 Jan 2022 14:52:55 +0000

Today you will learn strings and numbers manipulation in PHP.

This PHP crash course is free and will be posted here on dev.to. I'll be releasing a new article/post every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

String in PHP

Now let's see in a little more detail how to create and manipulate Strings with PHP.

A String can be created with single or double quotes

$name = 'Mike';

// or

$name = "Mike";

The declaration with double quotes allows you to do interpolation.

// Display the content of a variable
echo "Hello $name";
// Hello Mike

// or some find this syntax easier to read
echo "Hello {$name}";
// Hello Mike

It is also possible to join two strings with the operator "." (point)

$name = 'Mike';

echo 'Hello ' . $name;
// Hello Mike

It is possible to read or modify a particular character using the brackets []

$message = "Hello World";

// Display
echo $message[0];
// H

// Or modify
$message[1] = 'a';
// Hallo World

Here the first character is at position 0, the second at position 1, etc.

It is possible to access stating from the end.

$message = "Hello World";

echo $message[-1];
// d

Position -1 represents the last character, -2 the second last, and so on.

Heredoc

This syntax allows you to enter a string on several lines

$html = <<<HTML
<h1>This is a title</h1>
<p>This is a paragraphe</p>
HTML;

The $html variable will include all the text between the two HTML keywords. Including spaces and newlines.

Handling the Strings

PHP has several functions that allow you to transform the content of the String. Here are a few :

Uppercase and lowercase conversion

$name = 'Mike Taylor';

echo strtolower($name); 
// mike taylor

echo strtoupper($name);
// MIKE TAYLOR

Remove white space before and after a string

$message = '  Hello World        ';

echo trim($messsage);
// Hello World

Replace part of a string with another

$message = 'I love dog';

echo str_replace('dog', 'cat', $message);
// I love cat

Retrieve the number of characters in a string

$name = '';
echo strlen($name);
// 0

$name = 'Mike Taylor';
echo strlen($name);
// 11

Check if the string contains certain characters

$message = 'I love dogs and cats';

echo str_contains($message, 'dogs');
// true

If the string contains ‘dog’ the function will return true otherwise it will return false

The use of this kind of function will be more obvious when we study the conditional statement (if)

PHP has several functions for handling strings. Before creating your own function, do a little research in the documentation because there is a good chance that this function already exists.

Number in PHP

Numbers are used to perform mathematical operations such as addition, subtraction, multiplication, and division.

$value = 10;

echo $value + 5;
// 15

echo $value - 2;
// 8

echo $value * 2;
// 20

echo $value / 2;
// 5

Operator priority https://www.php.net/manual/en/language.operators.precedence.php

When we do multiple operations PHP will take into account the priority of the operators. That is, the order in which the values should be analyzed. Here is an example:

echo 1 + 5 * 3
// 16

Here the answer will be 16 and not 18. because the multiplication "*" has a higher priority compared to the addition "+".

Parentheses can be used to force the priority, if necessary.

echo (1 + 5) * 3
// 18

Syntax increment

It is possible to do an incrementation in three ways:

// Increment, long method

$value = 10;

$value = $value + 1;

echo $value;
// 11

// Increment, sort method

$value = 10;

$value += 1;

echo $value;
// 11

// Increment, shorter method

$value = 10;

$value++;

echo $value;
// 11

It is also possible to decrement

$value -= 1;

// ou
$value--;

Round

It is possible to round to the nearest whole number

$value = 10.52;

echo round($value);
// 11

It is also possible to specify the number of digits to keep after the period.

$value = 10.5278;

echo round($value, 2);
// 10.53

Random number

The rand function allows you to create a random integer whose value will be included between the values of the two parameters.

echo rand(10, 100); 
// 89

Readability of numbers

You can use the character _ as a separator. This helps to make the number easier to read.

$value = 1_000_000_000
// 1000000000

Conclusion

That's it for today, I'll be releasing a new article every two days or so. To be sure not to miss anything you can follow me on twitter: Follow @EricTheCoder_

Modern PHP crash course

Eric The Coder — Tue, 11 Jan 2022 09:49:32 +0000

Welcome to this modern PHP crash course. Why modern? PHP has been around since 1994 and has evolved considerably since then. Now, at version 8.1, PHP is a complete language and perfectly suited to modern web development.

In this crash course we will cover all the important aspects to know about PHP in 2022.

Once the course is finished, you will be able to create your first PHP applications and also you will have sufficient knowledge in PHP to continue your training with a PHP framework like Laravel and / or Symfony.

The crash course is free and will be posted here on dev.to. I'll be releasing a new article/post every two days or so. To not miss anything, you can follow me on twitter: Follow @EricTheCoder_

What is PHP? Why PHP?

PHP is an object oriented server side programming language. That is used to develop web applications.

PHP is the most widely used server programming language on the web today. Just under 80% of websites have PHP code. It's enormous! PHP is not going to disappear anytime soon.

PHP has evolved a lot in recent years. The addition of object oriented and several other modern concepts have dramatically changed the way PHP web applications are coded.

PHP is now used by millions of websites. Including Facebook, Wordpress, Wikipedia, Tumblr, Slack and many more.

The PHP community is very large, very dynamic and inclusive.

PHP can also rely on high quality frameworks like Symfony and Laravel (and several others). These frameworks allow you to develop web applications quickly and reliably.

In short, with PHP you can carry out small, big and very big projects. PHP can handle a few clicks per day or millions of clicks per day.

PHP Installation

Installing PHP can be tricky at times, don't be put off by this task.

If you want to start the training right away and do the installation later, it is possible to use the site https://replit.com/languages/php7 in order to execute PHP code from your browser.

Install PHP on your computer

You will need PHP version 8.1

To check which version is installed on your machine, you can

run this command from the terminal:

$ php -v

If PHP is missing or if the installed version is lower than PHP 8.1 you will need new install:

Here are the link for PHP installation:

MacOS (hombrew): https://www.php.net/manual/en/install.macosx.packages.php

Windows (XAMPP): https://www.apachefriends.org/index.html

For more details, see the official PHP documentation: https://www.php.net/manual/fr/install.php

PHP Basic concepts

For this tutorial we will create a folder to place all our files for the examples to come.

$ mkdir demo-php
$ cd demo-php

From this folder we will create a file named index.php

$ code index.php

This command will open vscode and create an index.php file.

Note that for this crash course we will be using Visual Studio Code but this is not a prerequisite. You are free to use your favorite editor.

On the first line of the file type

<?php

This tag will tell the PHP server that all subsequent lines are PHP code that the server should execute.

So we can now start writing PHP code and to start, nothing better than the classic Hello World!

<?php

echo 'Hello World';

The echo function allow text and even html to be display in the browser current page.

To test this code you can run the PHP web server which is included with PHP

$ php -S localhost:5000

The -S option starts the web server on localhost:5000

If you open a browser and go to the address http://localhost:5000, the PHP server will render the default file, index.php so you will see:

Hello World

HTML and PHP

Note that in a PHP file it is possible to have HTML codes mix with PHP codes

<h1>
    <?php echo 'Hello World'; ?>
</h1>

This code is perfectly valid. The ?> tag indicates the end of the PHP code.

It would also be possible to have several sections of PHP code

<h1>
    <?php echo 'Hello World'; ?>
</h1>

<h2>
    <?php echo 'Sub title'; ?>
</h2>

Although PHP can be mixed with HTML, it is considered good practice to separate PHP code and HTML code each into its own file. We will come back to this concept later.

Variables

Variables are used to store different values that you want to process in your code.

Once the variable is stored in program memory, it can be used later.

For example, suppose you want to store the username, you can use a variable and give it the name: $name and set its content equal to 'Mike Taylor'

$name = 'Mike Taylor';

Note that in PHP:

The name of a variable begins with a $ sign
A character string is surrounded by quotes.
We do not have to specify the type of variable (eg: string). PHP is an interpreted language. It automatically recognizes the data type based on the value stored in it.
On the other hand, it is possible to specify the type of the variable when declaring it. We will see this concept a little later.

Here are the 4 basic types of PHP variables and the syntax to create them

// string
$fullName = 'Mike Taylor';

// integer 
$count = 20;

// float (decimal number)
$bookPrice = 15.80;

// booleans
$isActive = true;
$isAdminUser = false;

PHP also has more advanced types of variables like arrays and classes. We'll cover all of this in detail later.

Finally, PHP also has some special types, like “null” which means no values.

At this point you should be able to understand that these two variables do not have the same content.

$value = '100';

$value2 = 100;

$value is a string variable which contains de text ‘100’ as content. This variable is not a number that can be used in a mathematical operation.

$value2 is an integer variable which has the number 100 as content. This variable is a number and can therefore be used for mathematical operations.

Constant

Constants, are variables whose value cannot be changed in any way. There are two ways to create them.

const MAX_USERS = 50;

define('MAX_USERS', 50);

A constant does not start with a $ sign and by convention, constants are defined in uppercase letters. After creation, if you try to assign another value to it, PHP will give you an error.

Typecasting

PHP automatically determines the type of the variable at runtime.

Output

In PHP there are several ways to display the content of a variable, here are some of them:

echo $name; (Displays the value)
var_dump($isAdmin); (Displays the type of the variable as well as the value)
print_r($items); (Displays the value legibly)

Determine the type of a variable

It is possible to get the type of a variable with the gettype() function

echo gettype($name); // string
echo gettype(20); // integer
echo gettype(9.95); // double
echo gettype(true); // boolean

We can also check if the variable is of a certain type with the functions is_init(), is_float(), is_string() and is_bool()

echo is_int($name); // false
echo is_float(12.5); // true
echo is_string($name); // true
echo is_bool(10); // false

Force type (cast)

It is possible to force PHP to use a particular type and if necessary force the conversion. To do this, you must add the type in parentheses before the variable or the function.

$age = (int)readline('Your age:');
echo 'Your age is'. (string)$age;

Here the cast (int) will force an integer as the return value of the readline() function. The cast (string)$age will convert the integer to a string before displaying it.

Comments

To leave a comment in the code. That is to say a line which will not be executed, you can use one of the following two techniques:

// This is a single line comment

/*
This is a comment
on several lines
*/

Naming convention

Here are some conventions that we will use to create our code:

$firstName = 'Mike';  // variables name will be camelCase
function updateProduct() // functions name will be camelCase
class ProductItem // class name will be StudlyCaps
const ACCESS_KEY = '123abc'; // all upper case with underscore separators

For more details on naming conventions yon can check the PRS web site: https://www.php-fig.org/psr/

Conclusion

That's it for today, I'll be releasing a new article every two days or so. To be sure not to miss anything you can follow me on twitter: Follow @EricTheCoder_

PHP cheat sheet (updated to PHP 8.1)

Eric The Coder — Mon, 06 Dec 2021 17:07:42 +0000

Follow me!: Follow @EricTheCoder_

Here is my cheat sheet I created along my learning journey. If you have any recommendations (addition/subtraction) let me know.

PHP local server

php -S localhost:3000

Comments

// one line comment

/*
This is a multiple-lines comment block
that spans over multiple
lines
*/

Naming conventions

// PHP opening/closing tag
<?php
  echo "Hello World";
?>
// if no closing tag the rest of the file will be considered PHP

// Short syntax for PHP echo
<?= "Hello World" ?>

//Enable strict typing (first line of your PHP file)
<? declare(strict_types=1);

// Include a PHP file
require 'app/Product.php'

// Create a namespace
namespace App;

// Use a namespace
use App\Product;

$firstName = 'Mike'  // camelCase
function updateProduct() // camelCase
class ProductItem // StudlyCaps
const ACCESS_KEY = '123abc'; // all upper case with underscore separators

Output & Input

echo 'Hello World';

// Debug output
var_dump($names);
print_r($products);

// Input from console
$name = readline('What is your name : ');

Variables Declaration

$name = 'Mike'; //string
$isActive = true; //boolean
$number = 25; //integer
$amount = 99.95; //float
$fruits = ['orange', 'apple', 'banana'] //array
const MAX_USERS = 50; //constant
define('MAX_USERS', 50); //constant

// Assign 'by reference' with the & keyword
$name_2 = &$name_1

// Type conversion
$age = (int)readline('Your age: ');
echo 'Your age is' . (string)$age;

echo gettype($age); // int

echo is_int($age) // true
echo is_float(12.5) // true
echo is_string($name) // true

Strings

// String can use single quote
$name = 'Mike'
// or double quote
$name = "Mike"

// Double quote string can escape characters \n = new line  \t = tab  \\ = backslash
echo "Hello Mike\nHello David";

// Double quote string can do interpolation
echo "Hello $name";

// string concat
echo 'Hello ' . $name;

// string length
echo strlen($name);

// Remove space(s) before and after
echo trim($text)

// Convert to lowercase / uppercase
echo strtolower($email);
echo strtoupper($name);

// Converts the first character to uppercase
echo ucfirst($name);  // 'Mike' 

// Replace text a by text b in $text
echo str_replace('a', 'b', $text);

// String Contains (PHP 8)
echo str_contains($name, 'ke')  # true

// Find numeric position of first occurrence 
$pos = strpos($name, 'k'); # 2

// Returns portion of string (offset / length)
echo substr($name, 0, $pos); # Mi

Numbers


// Shortcut addition assignment
$value = 10
$value++ // 11
// or
$value += 1 // 11

// Shortcut subtraction assignment
$value = 10
$value-- // 9
// or
$value -= 1 // 9

// Check if numeric
echo is_numeric('59.99'); # true

// Round a number
echo round(0.80);  // returns 1

// Round a number with precision
echo round(1.49356, 2));  // returns 1.49

// Random number 
echo(rand(10, 100)); # 89

Conditionals

// If / elseif / else
if ($condition == 10) {
    echo 'condition 10'
} elseif  ($condition == 5) {
    echo 'condition 5'
} else {
    echo 'all other conditions'
}

// And condition = &&
if ($condition === 10 && $condition2 === 5) {
    echo '10 and 5'
}

// Or condition = ||
if ($condition === 10 || $condition2 === 5) {
    echo '10 or 5'
}

// One line 
if ($isActive) return true;

// Null check
if (is_null($name)) {
    do something...
}

//Comparaison operation
== // equal no type check
=== // equal with type check
!= //not equal
|| //or
&& //and
> //greater than
< //less than

// Ternary operator (true : false)
echo $isValid ? 'user valid' : 'user not valid';

//Null Coalesce Operator
echo $name ?? 'Mike';  //output 'Mike' if $name is null

//Null Coalesce Assignment
$name ??= 'Mike';

// Null Safe Operator (PHP 8) will return null if one ? is null
echo $user?->profile?->activate();

// Null Safe + Null Coalesce (if null will return 'No user profile')
echo $user?->profile?->activate() ?? 'Not applicable';

//Spaceship operator return -1 0 1
$names = ['Mike', 'Paul', 'John']
usort($names, function($a, $b) {
    return $a <=> $b;
}
// ['John', 'Mike', 'Paul']

// Return false when convert as boolean
false, 0, 0.0, null, unset, '0', '', []

// Compare same variable with multiple values
switch ($color) {
    case 'red':
        echo 'The color is red';
         break;
    case 'yellow':
        echo 'The color is yellow';
        break;
    case 'blue':
        echo 'The color is blue';
        break;
    default:
        echo 'The color is unknown';
}

// Match Expression (PHP 8)
$type = match($color) {
    'red' => 'danger',
    'yellow', 'orange' => 'warning',
    'green' => 'success',
    default => 'Unknown'
};

// Check if variable declare
isset($color['red']);  # true

Loops and Iterations

//for loop
for ($i = 0; $i < 20; $i++) {
    echo "i value = " . i;
}

//while loop
$number = 1;
while ($number < 10) {
    echo 'value : ' . $number ;
    $number += 1;
}

//do while
$number = 1;
do {
    echo 'value : ' . $number ;
    $number += 1;
} while ($number < 10);

// foreach with break / continue exemple
$values = ['one', 'two', 'three'];
foreach ($values as $value) {
    if ($value === 'two') {
        break; // exit loop
    } elseif ($value === 'three') {
        continue; // next loop iteration
    }
}

Arrays

//Array declaration can contain any types
$example = ['Mike', 50.2, true, ['10', '20']];

//Array declaration
$names = ['Mike', 'Peter', 'Shawn', 'John'];

// Direct access to a specific element
$name[1] //output Peter

// How to access an array in an array
$example[3][1] // 20

//add a element to an array
$names[] = 'Micheal';

// Array merge
$array3 = array_merge($array1, $array2);

// Merge with spreading operator (also work with associative array)
$array3 = [...$array1, ...$array2];

// Array Concat with Spread Operator
$names = ['Mike', 'Peter', 'Paul'];
$people = ['John', ...$names]; // ['John', 'Mike', 'Peter', 'Paul']

//Remove array entry:
unset($names['Peter']);

//Array to string
echo implode(', ', $names) //output Mike, Shawn, John, Micheal

// String to Array
echo explode(',', $text); // ['Mike', 'Shawn', 'John']


//loop for each array entry
foreach($names as $name) { 
   echo 'Hello ' . $name;
}

// Number of items in a Array
echo count($names);  

//Associative array declaration (key => value):
$person = ['age' => 45, 'genre' => 'men'];

//Add to ass. array:
$person['name'] = 'Mike';

//loop ass. array key => value: 
foreach($names as $key => $value) { 
   echo $key . ' : ' . $value
}

// Check if a specific key exist
echo array_key_exists('age', $person);

// Return keys
echo array_keys($person); // ['age', 'genre']

// Return values
echo array_values($person) // [45, 'men']

//Array filter (return a filtered array)
$filteredPeople = array_filter($people, function ($person) {
    return $names->active;
})

// Array map (return transform array):
$onlyNames = array_map(function($person) {
    return ['name' => $person->name];
}, $people)

# Search associative array
$items = [
        ['id' => '100', 'name' => 'product 1'],
        ['id' => '200', 'name' => 'product 2'],
        ['id' => '300', 'name' => 'product 3'],
        ['id' => '400', 'name' => 'product 4'],
    ];

# search all value in the 'name' column
$found_key = array_search('product 3', array_column($items, 'name'));
# return 2

Functions

//function declararion
function name($firstName, $lastName = 'defaultvalue') {
    return "$firstName $lastName"
}

//function call
name('Mike', 'Taylor');

//function call with named parameters (PHP 8)
name(firstName: 'Mike', lastName: 'Taylor'); // order can change

//function variables params
function name(...$params) {
    return $params[0] . “ “ . params[1];
}

// Closure function
Route::get('/', function () {
     return view('welcome');
});

// Arrow functions
Route::get('/', fn () => view('welcome');


// Typed parameter and typed return
function display(string $first, string $last) : string {
    return "$first $last";
}

// Typed or null
function display(?string $name) {
    ...
}

// Union type (or)
function display(string|int $data) {
    ...
}

// Intersection type (and)
function count_and_interate(Iterator&Countable $value) {
    ...
}

// Return any type (mixed)
function logInfo(string $info) : mixed {
    ...
}

// No return (void)
function logInfo(string $info) : void {
    ...
}

Enumerations

// Declaration
enum InvoiceStatus
{
    case Sent;
    case Paid;
    case Cancelled;
}

// The enum can then be use as a type
function printInvoiceStatus(InvoiceStatus $status)
{
    print($status->name);
}

printInvoiceStatus(InvoiceStatus::Sent);
// Sent

// enum with return value and public function exemple
enum InvoiceStatus : int
{
    case Sent = 0;
    case Paid = 1;
    case Cancelled = 2;

    public function text() : string
    {
        return match ($this) {
            self::Sent => 'Sent',
            self::Paid => 'Paid',
            self::Cancelled => 'Cancelled'
        };
    }
}

function getInvoiceStatus(InvoiceStatus $status)
{
    print($status->text());
    print($status->value);
}

getInvoiceStatus(InvoiceStatus::Paid);
// Paid1

Files

// Get the current dir
$current_dir = __DIR__;

// Check if file exist
if (file_exists('/posts/first.txt')) {
  do some stuff
}

// Read file content into one variable
$post = file_get_contents($file);

//File read
$file = fopen("test.txt", "r");

//Output lines until EOF is reached
while(! feof($file)) {
  $line = fgets($file);
  echo $line. "<br>";
}
fclose($file);

// File write (csv)
$file = fopen('export.csv', 'a');
$array = ['name' => 'Mike', 'age' => 45];

//Write key name as csv header
fputcsv($file, array_keys($array[0]));

//Write lines (format as csv)
foreach ($array as $row) {
    fputcsv($file, $row); 
}
fclose($file);

Errors

//Throw Error
if (someCondition) {
    throw new Exception('Data format error');
}

//Catch the Error
try {
  $db->checkData($data);
} catch (Exception $e) {
    echo $e->getMessage();
}

OOP

//class declaration
class Person 
{
}

// object instantiation
$person = new Person

//class properties and constructor
class Person 
{
   protected $firstName;
   protected $lastName;
   public function __construct($firstName, $lastName) {
        $this->firstName = $firstName;
        $this->lastName = $lastName
   }

// Constructor Property Promotion (PHP 8)
class Person 
{
    public function __construct(protected $firstName, protected $lastName) 
    {

    }

// Getter and Setter
class Person
{
    private $name;

    public function setName($name){
        if(!is_string($name)){
            throw new Exception('$name must be a string!');
        }
        $this->name = $name;
    }

    public function getName(){
        return $this->name;
    }
}

// Readonly properties (PHP 8.1)
class Person 
{
    public function __construct(
        public readonly string $firstName, 
        public readonly string $lastName
    ) {

    }
}

//static constructor
public static function create(...$params) {
    return new self($params)
}
$person = Person::create(‘Mike’, ‘Taylor’);

// Static Method
class greeting {
  public static function welcome() {
    echo "Hello World!";
  }
}

// Call static method
greeting::welcome();

// Static method call
class greeting {
  public static function welcome() {
    echo "Hello World!";
  }

  public function __construct() {
    static::welcome();
  }
}
new greeting();

// Static constant
class Connection
{
  const MAX_USER = 100;
}
echo Connection::MAX_USER # 100

// class inheritance
class Customer extends Person
{
    public function name()
    {
        parent::name();
        echo 'Override method';  
    }
}

// self keyword reference current class (not modify by inheritance late binding like static will be)
self::welcome();

// Interface
interface Animal {
  public function makeSound();
}

class Cat implements Animal {
  public function makeSound() {
    echo "Meow";
  }
}
$animal = new Cat();
$animal->makeSound();

//Trait (mix-in)
trait HelloWorld {
    public function sayHello() {
        echo 'Hello World!';
    }
}

class Greetings {
    use HelloWorld;
}
$object = new Greetings();
$object->sayHello();

Follow me!: Follow @EricTheCoder_

Python FastAPI crash course: Part 3

Eric The Coder — Mon, 29 Nov 2021 12:36:37 +0000

Here is a crash course (series of articles) that will allow you to create an API in Python with FastAPI.

To not miss anything follow me on twitter: https://twitter.com/EricTheCoder_

POST

So far we have covered the READ of CRUD, now let's see the "Create".

Here it is no longer a question of reading data but of creating a new one.

To create a new product we need to send some information to the server, and to do this we will need to use the HTTP POST action

POST www.example.com/products

The POST action sends data from the client to the server.

Example

We will do an example and add the product "MacBook" to our existing product list.

Here is the expected result:

products = [
    {"id": 1, "name": "iPad", "price": 599},
    {"id": 2, "name": "iPhone", "price": 999},
    {"id": 3, "name": "iWatch", "price": 699},
    {"id": 4, "name": "MacBook", "price": 1299},
]

To do a POST with FastAPI here is the code you must use

@app.post("/products")
def create_product(product: dict, response: Response):
    product["id"] = len(products) + 1
    products.append(product)
    response.status_code = 201
    return product

Let's take this code line by line:

@app.post("/products")

This code is used to specify to FastAPI that this request will be a POST "/products" action

def create_product(product: dict, response: Response):

This code is used to define the function that will be launched when the server receives the "POST/products" request.

The function contains two parameters, one for the product and the other for a reference to the response object.

Note that when performing a POST action, the data to be sent must be included in the body of the request and must be in JSON text format.

In this example we see all the power and ease of FastAPI. FastAPI knows it is a POST request, so it will automatically take the JSON that is in the request body, convert it to a Python dictionary and place the result in the first parameter (product).

So we can then use this "product" parameter to add the product to our product list.

product["id"] = len(products) + 1
products.append(product)

Once the product has been added successfully, the appropriate status code should be returned.

response.status_code = 201

This code is used to return the status code 201 (Created). Which indicates that the product is indeed created successfully.

Finally, by convention, the new product is always returned with the response.

return product

Testing an HTTP Post action

Web browsers do not allow you to initiate a POST request. So it will not be possible to test this new API from the browser.

There are several other ways to do this. We could use software like Postman and test our requests from Postman.

One of the advantages of FastAPI is that it automatically generates documentation for our API. This documentation allows users to understand how to use our API, what are the available URL paths and also to execute requests.

We will therefore be able to use the documentation to test our API

As mentioned, in the case of our API the documentation is created automatically. To view it, start the server

$ uvicorn first-api:app --reload

and visit /docs

http://127.0.0.1:8000/docs

The documentation will be displayed on the screen!

To test a URL path it's very simple, just click on the path name and FastAPI will reveal an interface allowing you to test this endpoint.

For example if you click on POST /products you will see appear

You can then click on "Try it out", enter the data to add in the "Request body" section (see example below)

The data is in JSON text format

{"name": "MacBook", "price": 1299}

Finally click "Execute", the doc send the POST request to your FastAPI server

The response status code as well as the response itself will also be displayed on the page.

This automatic documentation is yet another great demonstration of the power and ease of FastAPI.

If you wish, you can click on all the endpoints one after the other in order to test them.

Validation

Let's go back to the last example we created

@app.post("/products")
def create_product(product: dict, response: Response):
    product["id"] = len(products) + 1
    products.append(product)
    response.status_code = 201
    return product

The @app.post() function works but has several shortcomings. In fact, there is no validation and no error message is returned if this validation does not pass.

For example, to create a new product we need the "name" and "price". What happens if only the "name" is sent but not the "price"?

Or what if the "price" is not a number format.

I could give you several more examples but I think you understand the concept.

To make these validations and return the associated error messages, we would have to add a lot of code to our function. And this code would have to be repeated for each action and each resource. All of this would greatly complicate our application.

Fortunately, FastAPI is named "Fast" API. So there is a very simple way to implement an automatic validation system. This system is the schema!

The schema

Schemas are data models that FastAPI uses to validate our functions.

For example we could define a schema like this:

from pydantic import BaseModel

class Product(BaseModel):
    name: str
    price: float

This data model is very easy to understand. We have a "Product" entity which contains the "name" and "price" attributes. We can even define what the type attributes are.

Once we have defined our data model, we can modify our @app.post() function

@app.post ("/products")
def create_product(new_product: Product, response: Response):
    product = new_product.dict()
    product["id"] = len(products) + 1
    products.append(product)
    response.status_code = 201
    return product

We replaced the "dict" type parameter with a "Product" type parameter.

Once this change is made, if you test this function, you will see that FastAPI now applies automatic validation and will return an error if what you send does not respect the "Product" model.

PUT

The PUT action is used to modify an existing resource. Like the POST action, the data to be modified must be sent with the request.

Here is an example of a PUT function

@app.put("/products/{id}")
def edit_product(id: int, edited_product: Product, response: Response):
    for product in products:
        if product["id"] == id:
            product['name'] = edited_product.name
            product['price'] = edited_product.price      
            response.status_code = 200
            return product
        else:
            response.status_code = 404
            return "Product Not found"

There is nothing really new here. These are exactly the same concepts that we discovered a little earlier.

DELETTE

The DELETE action allows you to delete a resource. Here is the code to implement this action

@app.delete("/products/{id}")
def destroy_product(id: int, response: Response):
    for product in products:
        if product["id"] == id:
            products.remove(product)
            response.status_code = 204
            return "Product Deleted"
        else:
            response.status_code = 404
            return "Product Not found"

Database

The code you have just created to implement CRUD is fine, but it still lacks an important notion and that is to link the resource with a database. The next section will explain how to do it step by step.

Conclusion

That's all for today, follow me on twitter: https://twitter.com/EricTheCoder_ to be notified of the publication of the next article.

Python FastAPI crash course: Make your first CRUD API

Eric The Coder — Tue, 23 Nov 2021 13:34:05 +0000

Here is a crash course (series of articles) that will allow you to create an API in Python with FastAPI.

I will publish a new article about every two days and little by little you will learn everything there is to know about FastAPI

To not miss anything follow me on twitter: https://twitter.com/EricTheCoder_

Create a CRUD API

Now we are going to create an API that will be closer to what you will need to create in a real project.

CRUD is an acronym that stands for Create, Read, Update, and Delete. These actions are the actions most often used when manipulating data.

Here is a concrete example. Consider a data table containing products:

products = [
    {"id": 1, "name": "iPad", "price": 599},
    {"id": 2, "name": "iPhone", "price": 999},
    {"id": 3, "name": "iWatch", "price": 699},
]

So you might have URL paths to perform CRUD actions on this product board.

Here are some examples:

Create a new product

POST www.example.com/products

Read all products

GET www.example.com/products

Read a particular product (e.g. with id = 2)

GET www.example.com/products/2

Modify a specific product (e.g. with id = 2)

PUT www.example.com/products/2

Delete a specific product (e.g. with id = 2)

DELETE www.example.com/products/2

Note that the name and structure of URL paths are not random. It is a convention that is used in the creation of APIs.

This is why to retrieve a particular product you must specify its id directly in the path:

GET www.example.com/products/2

FastAPI allows you to read this path and extract the relevant information. We will see this concept shortly.

First step

In your file first-api.py replace the current content with this one

from fastapi import FastAPI

app = FastAPI()

products = [
    {"id": 1, "name": "iPad", "price": 599},
    {"id": 2, "name": "iPhone", "price": 999},
    {"id": 3, "name": "iWatch", "price": 699},
]

@app.get("/products")
def index():
    return products

To start the server and test your API, type in the terminal (if you haven't already done so).

$ uvicorn first-api:app --reload

So you can then visit: http: //127.0.0.1: 8000/products

The list of all products will be displayed in JSON format:

[
  {
    "id": 1,
    "name": "iPad",
    "price": 599
  },
  {
    "id": 2,
    "name": "iPhone",
    "price": 999
  },
  {
    "id": 3,
    "name": "iWatch",
    "price": 699
  }
]

So we created the READ of our CRUD API. Now let's see the other URL paths

Extract the "id" from the URL path

To read all a particular product we need to extract the id from the url path. For example with the path "/products/2" how to extract the 2?

FastAPI allows to automatically send part of the path in a variable

@app.get("/products/{id}")
def index(id: int):
    for product in products:
        if product["id"] == id:
            return product
    return "Not found"

In the @app.get() the part represented by {id} will be sent in the variable "id" of the function index(id: int)

It is then possible to use this "id" variable to find the right product.

Note that the "id" parameter is completed with ":int" This addition allows you to specify the type of the variable, in this case an integer.

Why use a type in the parameter? This allows FastAPI to validate the incoming data.

For example the path "/products/abc" would return an error because "abc" is not an integer

Status Code

When the HTTP server returns a response, it always returns a status code with the response.

All HTTP response status codes are separated into five classes or categories. The first digit of the status code defines the response class, while the last two digits have no ranking or categorization role. There are five classes defined by the standard:

1xx information response - request has been received, process in progress

2xx successful - the request was received, understood and accepted successfully

3xx redirect - additional steps must be taken in order to complete the request

Client error 4xx - request contains bad syntax or cannot be fulfilled

Server error 5xx - the server failed to respond to an apparently valid request

Here are some examples of status code

200 OK

201 Created

403 Forbidden

404 Not Found

500 Internal Server Error

In our last FastAPI example, if the product is not found the path will return "Not found" however the status code returned will always be "200 OK"

By convention when a resource is not found it is necessary to return a status "404 Not Found"

FastAPI allows us to modify the status code of the response

from fastapi import FastAPI, Response

...

@app.get("/products/{id}")
def index(id: int, response: Response):
    for product in products:
        if product["id"] == id:
            return product

    response.status_code = 404
    return "Product Not found"

To do this we must add 3 lines to our code:

First we need to import the Response object
Then add the "response: Response" parameter to our function
And finally change the status to 404 if the product is not found

Note that the "response: Response" parameter may seem strange to you, indeed how is it possible that the "response" variable contains an instance of the "Response" object without even having created this instance?

This is possible because FastAPI creates the instance for us in the background. This technique is called "Dependency Injection".

No need to understand this concept, just using it is enough for now.

Extract the "Query Parameters"

Take for example the following path:

/products/search/?name=iPhone

This path requests the list of all products which contain the word "iPhone"

The "?Search=iPhone" is a Query Parameter.

FastAPI allows us to extract this variable from the URL path.

After the existing code, enter:

@app.get("/products/search")
def index(name, response: Response):
    founded_products = [product for product in products if name.lower() in product["name"].lower()]

        if not founded_products: 
        response.status_code = 404
        return "No Products Found"

        return founded_products if len(founded_products) > 1 else founded_products[0]

Just add the name of the variable as a parameter to the index() function. FastAPI will automatically associate Query Parameters with variables of the same name. So "?Name=iPhone" will end up in the parameter/variable "name"

Path declaration order

If you launch your server and try to visit the following URL path

http://127.0.0.1:8000/products/search?name=iPhone

You will probably get this error

{
  "detail": [
    {
      "loc": [
        "path",
        "id"
      ],
      "msg": "value is not a valid integer",
      "type": "type_error.integer"
    }
  ]
}

Why ? The error message states that the value is not of type integer? Yet if we look at our function, no value is of type integer? We only have a "name" parameter

In fact, the message speaks the truth. Here is all our code so far

from fastapi import FastAPI, Response

app = FastAPI ()

products = [
    {"id": 1, "name": "iPad", "price": 599},
    {"id": 2, "name": "iPhone", "price": 999},
    {"id": 3, "name": "iWatch", "price": 699},
]

@app.get("/products")
def index():
    return products

@app.get("/products/{id}")
def index(id: int, response: Response):
    for product in products:
        if product["id"] == id:
            return product

    response.status_code = 404
    return "Product Not found"

@app.get("/products/search")
def index(name, response: Response):
    founded_products = [product for product in products if name.lower() in product["name"].lower()]

        if not founded_products: 
        response.status_code = 404
        return "No Products Found"

        return founded_products if len(founded_products) > 1 else founded_products[0]

We have a route "/products/{id}" which is declared before the last route. The dynamic part of route "{id}" means that all routes that match "/products/*" will be executed with this code.

So when we ask for "/products/search/?Name=iPhone" FastAPI sends us to the second route because it matches "/products/*". The last function is never performed and never will be.

The solution? Reverse the routes, the order of the routes is essential for FastAPI. it is therefore important to place dynamic routes like "/products/{id}" last

from fastapi import FastAPI, Response, responses

app = FastAPI()

products = [
    {"id": 1, "name": "iPad", "price": 599},
    {"id": 2, "name": "iPhone", "price": 999},
    {"id": 3, "name": "iWatch", "price": 699},
]

@app.get("/products")
def index():
    return products

@app.get("/products/search")
def index(name, response: Response):
    founded_products = [product for product in products if name.lower() in product["name"].lower()]

        if not founded_products: 
        response.status_code = 404
        return "No Products Found"

        return founded_products if len(founded_products) > 1 else founded_products[0]

@app.get("/products/{id}")
def index(id: int, response: Response):
    for product in products:
        if product["id"] == id:
            return product

    response.status_code = 404
    return "Product Not found"

With the code in that order, if you revisit "/products/search?Name=iphone". You will have the following answer:

{
  "id": 2,
  "name": "iPhone",
  "price": 999
}

Conclusion

That's all for today, follow me on twitter: https://twitter.com/EricTheCoder_ to be notified of the publication of the next article (within two days).

Python FastAPI crash course

Eric The Coder — Sat, 20 Nov 2021 14:11:24 +0000

Here is a crash course (series of articles) that will allow you to create an API in Python with FastAPI.

I will publish a new article about every two days and little by little you will learn everything there is to know about FastAPI

To not miss anything follow me on twitter: https://twitter.com/EricTheCoder_

What is FastAPI?

FastAPI is a Python web framework that allows you to quickly build high performance APIs.

Why FastAPI?

Before FastAPI there were already several ways to create APIs with Python. Especially with Django Rest Framework and Flask. So why FastAPI?

Here is the list of the main advantages of FastAPI:

Very fast: The performance is superior to Django and Flask and is even comparable to the performance of NodeJS and GO
Fast to code: Build APIs 2-3 times faster
Easy: Easy to use and learn
Type annotation (Type hints): Facilitates validation, allows auto-completion and facilitates debugging
Automatic documentation: FastAPI generates documentation in Swagger UI and ReDoc format automatically.

Pre-requisites

To start coding with FastAPI you must have a basic programming knowledge with the Python language.

You should also make sure that you have an updated version of Python (version 3.6 or +)

From the terminal type this command to find out the version of Python installed on your machine.

$ python --version

or

$ python3 --version

If you don't have Python or a version earlier than 3.6, you can get the latest version of Python from the official website: https://www.python.org/downloads/

Code editor

For this tutorial, I'll be using Visual Studio Code: https://code.visualstudio.com/

It will be easier for you to follow me with this editor but it is really not a requirement.

Finally, if you are using vscode, make sure the Python extension is installed.

Creation of the virtual environment

When working on a Python project, we have to work with several libraries like FastAPI, Flask or Django, etc.

According to the date of creation of the project. It is possible for example that the FastAPI library is not exactly at the same version number in the other projects.

How to allow each project to have its own version of Python and its own versions of libraries?

We will be using virtual environments.

A virtual environment allows you to install Python and python libraries in a folder / project without this affecting the other folders / projects.

Python provides you with a system that allows you to create virtual environments.

Once the environment has been created and activated, all the libraries installed can be used only in the environment to which they belong.

How to create a virtual environment

Normally we place a virtual environment in the project folder.

Create and access a folder for our project

$ mkdir fastapi-demo
$ cd fastapi-demo

From this folder you can now create the virtual environment that will be attached to the project

$ python3 -m venv env

Here we launch python3 with the module option venv. env is the name we give to our virtual environment.

Once the virtual environment has been created, you can activate it:

MacOS / Linux

$ source env/bin/activate

Windows

$ env\Scripts\activate.bat

That's it that's all ! You now have a Python virtual environment created for your project. Normally the terminal will tell you that your environment is activated by displaying its name.

Note that to deactivate the virtual environment you must run

$ deactivate

For the rest of the tutorial, make sure the virtual environment is enabled before running any commands in the terminal.

Installing FastAPI

From the fastapi-demo folder and with the virtual environment enabled, run the following installation command:

$ pip install "fastapi[all]"

This command will install FastAPI and also install some optional dependencies like local server (uvicorn) to test FastAPi on your machine.

Once these libraries are installed, you can launch your open code editor on the current folder

$ code .

This command will launch Visual Studio Code open on the current folder

Reminder: What is an API?

API stands for Application Programming Interface.

In short, it is a program that can be used by another program, in order to allow applications to communicate with each other.

An API allows the server and the client to communicate with each other and to exchange information and data. The data exchanged is in structured text format (JSON).

The exchanges are made in the form of requests and responses:!

For example, the browser (client / frontend application) makes a specific request to a server:

GET www.example.com/products/3814

Can the server know how to handle this request? He can't. He won't know what to do with the request.

That's why we need to create an API. This is a server application that will determine how to respond to various requests for a specific resource.

Let's go back to the last example query:

GET www.example.com/products/3814

The customer wishes to obtain the information of the product no 3814

To respond to this request, we could create an API that would search for the 3814 product in a database and return this response to the customer in structured text (JSON) format.

{
  "id": 3814,
  "name": "iPhone 12",
  "qty": 29,
  "price": 799
}

Different type of requests

Note that all requests to servers are made through HTTP actions.

Here are the most commonly used HTTP actions

GET: GET requests are only used to retrieve data.

POST: POST requests are used to send data.

PUT: PUT requests are used to modify data.

PATCH: PATCH requests are used to partially modify data.

DELETE: DELETE requests are used to delete the specified data.

When we are dealing with a resource. For example Product. Each action on the Product resource has its own route

Here is an example route for each of the HTTP actions:

Create : POST www.example.com/

Read : GET www.example.com/products/3814

Update : PUT www.example.com/products/3814

Destroy : DELETE www.example.com/products/3814

The way to name these routes is no accident, it is in fact a convention that is followed by most developers.

Your first API

The theory is over, now let's see how to create your first API

From the code editor create a file named: first-api.py

Enter this code

from fastapi import FastAPI

app = FastAPI()

@app.get("/home")
def index():
    return {"message": "Hello World"}

app = FastAPI() allows to create an instance of FastAPI

The @app.get() decorator allows us to specify the url path and the HTTP (GET) action of our api.

The index() function will be executed each time a user visits the URL path specified by the @app.get() decorator, in this case the "/home" path

Note that the name of the "index()" function could be any name. It is according to your preference.

To start the server and test your first API, enter in the terminal

$ uvicorn first-api:app --reload

uvicorn is the local server. It takes as parameter the name of the file: the name of the FastAPI instance

The —reload option will restart the server each time the source file is modified.

So you can then visit: http://127.0.0.1:8000/home

The following response will be displayed:

{
  "message": "Hello World"
}

Well done! You have just created your first API

Last point. The path you created points to "http://127.0.0.1:8000/home". How to make it point to the "root path" aka "http://127.0.0.1:8000"

You must only use a back slash "/"

@app.get("/")

The back slash used alone means "root path"

Conclusion

That's all for today, follow me on twitter: https://twitter.com/EricTheCoder_ to be notified of the publication of the next article (within two days).

NodeJS + Express part 6: MongoDB database

Eric The Coder — Fri, 05 Nov 2021 11:51:42 +0000

Here is a series of articles that will allow you to create backend applications with NodeJS + Express.

This series is the continuation of my series on the basics of NodeJS. If you don't have basic knowledge of NodeJS read this series first: Introduction to NodeJS

Node.js is today a must, so it is essential for a developer to master it.

So I will publish a new article about every two days and little by little you will learn everything there is to know about Node.js + Espress

To not miss anything follow me on twitter: https://twitter.com/EricTheCoder_

MongoDB Database

In this section we will learn how to manipulate a MongoDB database from our API.

You probably know that there are several types of databases such as SQL databases and NoSQL databases.

The purpose of this article is not to explain in detail what a database is and how it works internally. So a minimum of database knowledge is required.

Today we are going to use MongoDB which is a NoSQL database

NoSQL databases contain collections that contain documents. For example a database could have the User collection and several documents which would each contain the information of a user such as for example: no, last name, first name, etc.

If you have experience with SQL databases, we could simplify this by saying that collections are tables and documents are rows and columns of tables.

MongoDB installation

MongoDB can be installed on your local machine or be used as a cloud database version.

In this tutorial we will create a MongoDB database from their cloud. https://www.mongodb.com/atlas

The service is free and does not require a credit card.

To have access to the MongoDB cloud and then be able to create your own database, go to https://www.mongodb.com/atlas and click on the "Try Free" button.

Choose the Atlas service, complete the questionnaire and click "Get started free"

Once your account is created, go to the control panel, you should see something like this.

Click on "Build a Database", then choose the "Free Shared" option and click on "Create". Then keep the default options except the last option which is "Cluster Name" and change the name to "NodeExpress". Finally click on "Create Cluster"

Create a database

Your MongoDB account is created and activated we will now create our database and our first collection

With your cluster now created, you should see something like this

To create a database and a collection. Click on "Browse Collection", then on "Add My Own Data". Finally enter the name of the database and the name of the collection and click on "Create"

Ready to code

To sum up, we created a MongoDB cloud account, created a free Cluster and created our first "Demo" database and finally our first "Products" collection.

Now we are ready to code our API and manipulate our database

Creation of the NodeJS project

We are now going to create our NodeJS project, I will give here the starting code (which comes from the previous articles).

Create a folder



$ mkdir demo-express-mongo
$ cd demo-express-mongo

Then install the ExpressJS package and nodemon



$ npm install express
$ npm nodemon

Note that as specified in the section on NodeJS, the nodemon package allows you to reload the server each time our code is modified.

In order not to repeat the concepts that we covered in the previous articles, we will start with the same code that we had at the end of the last article.

Create a controllers folder and create a products.js file with the following code



const products = require('../data.js')

const getProducts = ((req, res) => {
    res.json(products)
})

const getProduct = ((req, res) => {
    const id = Number(req.params.productID)
    const product = products.find(product => product.id === id)

        if (!product) {
        return res.status(404).send('Product not found')
    }
    res.json(product)
})

const createProduct = ((req, res) => {
    const newProduct = {
        id: products.length + 1,
        name: req.body.name,
        price: req.body.price
    }
    products.push(newProduct)
    res.status(201).json(newProduct)
})

const updateProduct = ((req, res) => {
    const id = Number(req.params.productID)
    const index = products.findIndex(product => product.id === id)
    const updatedProduct = {
        id: products[index].id,
        name: req.body.name,
        price: req.body.price
    }

    products[index] = updatedProduct
    res.status(200).json('Product updated')
})

const deleteProduct = ((req, res) => {
    const id = Number(req.params.productID)
    const index = products.findIndex(product => product.id === id)
    products.splice(index,1)
    res.status(200).json('Product deleted')
})

module.exports = {
    getProducts,
    getProduct,
    createProduct,
    updateProduct,
    deleteProduct
}

Then, create a "routes" folder and create the products.js file



const express = require('express')
const router = express.Router()

const  { 
    getProducts,
    getProduct,
    createProduct,
    updateProduct,
    deleteProduct 
} = require('../controllers/products.js')

router.get('/', getProducts)

router.get('/:productID', getProduct)

router.post('/', createProduct) 

router.put('/:productID', updateProduct) 

router.delete('/:productID', deleteProduct)

module.exports = router

Finally, create an app.js file with the following code



const express = require('express')
const app = express()
const products_routes = require('./routes/products.js')

app.listen(5000, () => {
    console.log('server is listening on port 5000')
})

app.use(express.json())
app.use('/api/products', products_routes)

So far nothing new, we are ready to continue this code by adding our MongoDB database

fichier .env

To connect to our MongoDB database we need the connection URL. MongoDB will provide us with this URL. The thing is, for obvious security reasons, we can't use this login URL directly in our code.

The connection URL must be placed in a file that will be out of reach of users during deployment.

To do this we will therefore create a file that will contain our connection URL. By convention this file named ".env" (dot env)

You can create this file at the root of the project and include the MongoDB connection URL



// .env 
MONGO_URI = 'mongodb+srv://<username>:<password>@nodeexpress.my1j7.mongodb.net/myFirstDatabase?retryWrites=true&w=majority'

To get your MongoDB login URL. Connect to your MongoDB cloud account and from the "Databases" menu click on "Connect", then choose the "Connect you application" option

MongoDB will show you your connection string, copy it and paste it into your .env file

In the connection string, replace and with your username and password MongoDB cloud user and also replace "myFirstDatabase" with the name of your database (ie "demo")

Communicating with MongoDB from NodeJS

There are several ways to communicate with your MongoDB database. For this project I decided to use the NodeJS package named "mongoose"

This packages makes it easy to link MongoDB and your API.

ODM

mongoose is an ODM (Object Document Mapping) which means that mongoose allows you to create an object (called a model) to represent and manipulate each of our collections.

This object (model) will contain several pre-defined functions that will allow you to easily handle the collection associated with this object.

Once the model is created, no need to manipulate the database, just use the methods of the model object and it will take care of communicating to the database. Suddenly, this pattern significantly increases the ease of handling the database.

Here is a quick example to visualize the concept



const products = await Product.find({})

In this code, the "Product" object / model uses the "find" method in order to read all the documents in the collection. The documents retrieved are sent to the "products" variable.

Creation of a mongoose model

We are now going to create a "Product" object / model

The first step is to install the mongoose package```jsx

npm install mongoose
npm install dotenv


While we are there we will also install the dotenv package. This package allows you to read the ".env" config file that we created earlier and load its variables into the current process.

Once the package is used, we can create our first mongoose model.

Create a "models" folder and create the Product.js file
```jsx


const mongoose = require('mongoose')

const ProductSchema = new mongoose.Schema({
    name:String,
    price: Float,
})

const Product = mongoose.model('Product', ProductSchema)

module.exports = Product

Mongoose models are created from the diagrams.

The diagram is used to define the structure of a document. (Kind of like the columns of a table in an SQL database).

In the last example we define the Product schema which will be the structure of the documents of the Products collection

The penultimate line allows you to create the Product model from the diagram



const Product = mongoose.model('Product', ProductSchema)

Connection to the database

Now that we have a mongoose model to work with, we must now establish the connection between mongoose and our MongoDB database.

Modify the app.js file to include the database connection code.



const express = require('express')
const mongoose = require('mongoose')
const app = express()
const products = require('./data.js')
const products_routes = require('./routes/products.js')

require('dotenv').config()

mongoose.connect(process.env.MONGO_URI)
    .then((result) => app.listen(5000))
    .catch((err) => console.log(Error))

app.use(express.json())
app.use('/api/products', products_routes)

Let's go back to the code with some explanations:

Send the contents of the .env file to the process.env object



require('dotenv').config()

Use the MONGO_URL to create a connection with your database



mongoose.connect(process.env.MONGO_URI)

If the connection is successful then start the NodeJS server otherwise display the error.



mongoose.connect(process.env.MONGO_URI)
    .then((result) => app.listen(5000))
    .catch((err) => console.log(Error))

CRUD API

Now that we have our connection to MongoDB, we can modify our "products" controller file (/controllers/products.js) and add the Product model methods to it.

In fact the operation of these methods is so simple and explicit that we do not need to explain them.



const Product = require('../models/Product.js')

const getProducts = ((req, res) => {
    Product.find({})
        .then(result => res.status(200).json({ result }))
        .catch(error => res.status(500).json({msg: error}))
})

const getProduct = ((req, res) => {
    Product.findOne({ _id: req.params.productID })
        .then(result => res.status(200).json({ result }))
        .catch(() => res.status(404).json({msg: 'Product not found'}))
})

const createProduct = ((req, res) => {
    Product.create(req.body)
        .then(result => res.status(200).json({ result }))
        .catch((error) => res.status(500).json({msg:  error }))
})

const updateProduct = ((req, res) => {
    Product.findOneAndUpdate({ _id: req.params.productID }, req.body, { new: true, runValidators: true })
        .then(result => res.status(200).json({ result }))
        .catch((error) => res.status(404).json({msg: 'Product not found' }))
})

const deleteProduct = ((req, res) => {
    Product.findOneAndDelete({ _id: req.params.productID })
        .then(result => res.status(200).json({ result }))
        .catch((error) => res.status(404).json({msg: 'Product not found' }))
})

module.exports = {
    getProducts,
    getProduct,
    createProduct,
    updateProduct,
    deleteProduct
}

However, if you want to know in detail how these methods work and the other methods available, see the mongoose documentation here: https://mongoosejs.com/docs/models.html

Test your API

You can now launch the Node.JS server and test the API



$ npx nodemon app.js

The server will be launched on port 5000 accessible to localhost: 5000

Using software like Postman, you can now test your API with the following queries:



GET localhost:5000/api/products

GET localhost:5000/api/product/<id>

POST localhost:5000/api/products 

PATCH localhost:5000/api/products/<id> 

DELETE localhost:5000/api/products/<id>

Note that for POST and PATH actions, you must send them with content in the body section of your request. Here is an example of content in JSON:



{

    "name": "iPhone12",

    "price": 899

}

Conclusion

That's all for today, follow me on twitter: https://twitter.com/EricTheCoder_ to be notified of the publication of the next article (within two days).