Forem: natamacm

Time Module with Example in Python

natamacm — Tue, 09 Jun 2020 14:51:58 +0000

The time module with its functions and examples in the Python programming language.

Python time Module
The time module is an integrated module in Python that has several features for time. For example, you can get the current date and time.

To use the time module, you have to import the time module (Python has many modules that let you build your program).

This module starts the time from the time of the recording. Epoch is history, beginning 1 January 1970. Epoch is history.

time()

The epoch time is returned by this function.

Python Example:

    # Import time module
    import time

    s=time.time()
    print('Total seconds since epoch:',s)

The program above outputs this:

Total seconds since epoch: 1576083939.5877264

This works in both the shell and in a script

ctime()

This Python function of the time module takes second as an argument and return time until the mentioned seconds.

Python Example:

    # Import time module
    import time

    st=1575293263.821704
    current_time=time.ctime(st)
    print('time since epoch:',current_time)

The program above outputs this:

time since epoch: Mon Dec  2 14:27:43 2019

sleep()

This function is used to pause the execution of the program for the time specified in the arguments.

Python Example:

    # Import time module
    import time

    print('Execution start time:',time.ctime())
    time.sleep(5)
    print('End execution time:',time.ctime())

The program above outputs this:

Execution start time: Tue Jun  9 16:40:56 2020
End execution time: Tue Jun  9 16:41:01 2020

strftime()

The strftime() function takes an argument and returns a string.

Python Example:

    # Import time module
    import time

    now_time=time.localtime() 

    tif=time.strftime("%m/%d/%Y, %H:%M:%S",now_time)

    print('The time since epoch:',tif)

The program above outputs this:

The time since epoch: 06/09/2020, 16:42:25

asctime()

The asctime() function takes a tuple of length nine as an argument and returns a string.

Python Example:

    # Import time module
    import time

    t=(2020,3,5,2,20,1,5,365,0)
    r=time.asctime(t)
    print("Time and date is:",r)

The program above outputs this:

Time and date is: Sat Mar  5 02:20:01 2020

yield keyword with example

natamacm — Tue, 09 Jun 2020 14:29:53 +0000

The Python keyword yield is a keyword in the python, is similar to return, both are in used in a function and yield returns values.

In this article we'll go over several examples of the yield keyword.

Syntax of yield keyword
The syntax of the yield keyword is

        def function():
            statements
            yield value
            statements

Python Example of yield:

        def sampleGenerate():
            yield 100
            yield 200
            yield 300

The yield keyword can be used both in the shell and from a script.

yield examples

Example 1:
Demonstrate the example with yield keywords by returning values multiple times on function calls.

    # python example of yield keyword

    def sample():
        yield 100
        yield 200
        yield 300

    # main code
    for value in sample():
        print(value)

The program above outputs this:

100
200
300

Example 2:
Find the squares of the numbers untill a maximum value. This can be done for various data types like integers or floats.

    # python yield keyword    
    def square():
        c = 1
        while True:
            yield c*c
            c += 1  

    for i in square():
        print(i)
        if i>=100:
            break

The program above outputs this:

timeit() Function with Example in Python

natamacm — Tue, 09 Jun 2020 14:08:04 +0000

You will learn about the Python timeit() function and shown an example in this tutorial. You can use it to calculate the time of code execution.

If you run any code, our code execution takes place with a number of background operations. When time() function counts on the time it does not take into consideration background operations going on to execute this code.

It subtracts time to get the necessary time at beginning and at the end. timeit() function has been developed to define the exact timing of each execution of the code.

This works both in the Python shell and from a script

timeit() example

Code execution time with timeit() function as an example:
We're going to type and hit python. It reacts with the python version you are using and it also confirms that you work in python.

Import statement:

    import timeit

Note we're not using the time module but timeit module.

If you will get a response like 'import' is not defined then go and check for system variable has been updated or not.

The program does a simple mathematical operation and find its execution timing by two methods.

# python example of timeit() function

# load module
import timeit

# time calcuation
print('x' *5)
print('x' + 'x' +'x' + 'x' + 'x' )
print(timeit.timeit("y = 'x' *3",number = 10000000))

The program above outputs this:

xxxxx
xxxxx
0.14592579402960837

Here you can put the value of number any number times as number times codeexecution required.

import timeit
print(timeit.timeit("xy = 'x' + 'x' + 'x' + 'x' + 'x' ", number=10000000))

The program above outputs this:

0.1387987380148843

This method describes the method to find execution timing manually. If you want to check an operation many times, instead of a loop you can use the method below.

timeit example

Now you will see how to perform the same tedious operation automatically?

import timeit

print(timeit.repeat("y = 'x'* 3", number = 10000000,repeat = 5))
print()
print(timeit.repeat("xy = 'x' + 'x' + 'x' + 'x' + 'x' " , number = 10000000,repeat = 5))

The program above outputs this:

[0.13703188695944846, 0.13094416703097522, 0.13312444603070617, 0.14463001501280814, 0.13111430197022855]

[0.1333333159564063, 0.1297284740721807, 0.12939571705646813, 0.1272417320869863, 0.12798011908307672]

Here you can see repetitions happen a number of times automatically.

Why timeit()?

Because of its precision, the timeit() function is the best way of finding time execution than time.

Many of our assumptions with regard to execution of the code in timeit() function were incorrect and have been rectified in the timeit() function as well.

If you are new to Python, I recommend this Python course.

What does the 'b' character do in front of a string literal in Python?

natamacm — Tue, 09 Jun 2020 13:39:37 +0000

Python sometimes has the 'b' character in front of a string. You are going to learn how to make a variable type as byte.

You will also learn what the 'b' character does in Python

Example

Consider the following examples,

    # variable definitions
    t_str = 'string'
    t_bytes = b'string'

    # print the types
    print(type(t_str))
    print(type(t_bytes))

You can try this both in the shell and from a script

The program above outputs this:

<class 'str'>
<class 'bytes'>

This means they are of a different type.

String vs bytes

As per the above example, the prefix of 'b' character to a string, makes the variable of data type bytes.

In the prefix 'b' before version 3, python ignored the variable bytes with 'b' in the later version. It can contain ASCII characters and it should be expressed bytes with an escape value of 128 or higher.

The bytes are the actual data. Strings are an abstraction. A byte is a collection of 8 bits, also known as binary

string isupper() and islower() methods with examples

natamacm — Tue, 09 Jun 2020 13:14:56 +0000

Python string isupper() and islower() methods with Examples.

Python isupper() and islower() are in-built methods in Python, that are used to check if a string is in uppercase or lowercase. Internally it uses an if statement that checks the characters.

String isupper() method

isupper() returns "true" if all characters of the string are uppercase characters.

Syntax:

 String.isupper()

Parameter:
None

Return type:

true - if all characters of the string are uppercase characters.
false - if any of the characters is not in uppercase character.

This works both in the Python shell and from a script

Python Example:

The example below shows how to use the isupper() method. The method is applied to the string directly.

So the methods isupper() and islower() both work with strings.

# s1 with all uppercase characters
s1 = "DEVTO"
print(s1.isupper())

# s2 with uppercase character, DOT, SPACE 
s2 = "DEV.TO"
print(s2.isupper())

# s3 with uppercase and lowercase characters
s3 ="DEV.to"
print(s3.isupper())

# s4 with all lowercase characters
s4 = "dev.to"
print(s4.isupper())

The program above outputs this:

    True
    True
    False
    False

2) String islower() method

The method islower() returns "true" if all characters of the string are lowercase characters.

Syntax:

 String.islower()

Parameter:
None

Return type:

true - if all characters of the string are lowercase characters.
false - if any of the characters is not in lowercase character.

Python Example:

# s1 with all uppercase characters
s1 = "DEVTO"
print(s1.islower())

# s2 with uppercase character, DOT, SPACE 
s2 = "DEV.TO"
print(s2.islower())

# s3 with uppercase and lowercase characters
s3 ="DEV.to"
print(s3.islower())

# s4 with all lowercase characters
s4 = "dev.to"
print(s4.islower())

The program above outputs this:

False
False
False
True

Read more:

How to get the directory of the currently running file?

natamacm — Fri, 22 May 2020 12:57:14 +0000

The Golang programming language makes it easy to build simple, reliable, and efficient software.

You can get the current directory of the program you are running (run golang).

So how to find out where the executable is?

As usual in programming languages, there are several ways to do this.
It's not Go specific, as you can have the same problem when programming C or C++.

To get the directory of the executable you can use "path/filepath.Dir".

For Go 1.8 and above you can use os.Executable for getting executable path

package main                                                                                                                               

import (                                                                                                                                   
    "fmt"                                                                                                                                  
    "os"                                                                                                                                   
    "path/filepath"                                                                                                                        
)                                                                                                                                          

func main() {                                                                                                                              
    ex, err := os.Executable()                                                                                                             
    if err != nil {                                                                                                                        
        panic(err)                                                                                                                         
    }                                                                                                                                      
    exePath := filepath.Dir(ex)                                                                                                            
    fmt.Println(exePath)                                                                                                                   
}

An alternative way to do this is with this code, it returns the current working directory:

package main

import (
    "fmt"
    "os"
)

func main() {
    pwd, err := os.Getwd()
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
    fmt.Println(pwd)
}

You can also do it this way:

import (
    "fmt"
    "log"
    "os"
    "path/filepath"
)

func main() {
    dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
    if err != nil {
            log.Fatal(err)
    }
    fmt.Println(dir)
}

Should I use Kivy or PyQT for GUI?

natamacm — Thu, 21 May 2020 14:46:07 +0000

Qt is a world-class, powerhouse GUI toolkit. Kivy is the new kid on the block. Kivy is beginner friendly and cross-platform, but so is PyQt. So what to choose?

On the desktop, PyQt is better because you can get a near-native look and feel easy and you have a simple gui designer.

But on mobile, it makes more sense to go with Kivy. Kivy is more oriented towards mobile interfaces.

PyQt is more oriented towards desktop software.

When it comes to licensing, PyQt requires payment for commercial applications. Kivy on the other hand is free for all types of applications.

Kivy is a python UI framework not a wrappper around an UI library. Pyqt on the other hand is a wrapper around the QT UI library. But PyQt is not only a UI library, it can also do networking, databases and other things.

PyQt is a mature module for building GUIs and other things, it is continuously developed and has been around for a long time. That means it's easy to find developers that have experience with PyQt/Qt.

Learning resources

So how do you get started with building GUI applications with Python?
First you should know Python programming itself. Then you can learn either GUI framework.

Here are some useful links for PyQt

For Kivy, these learning resources are available:

Which one should I use for GUI wxpython or pyqt?

natamacm — Thu, 21 May 2020 14:18:01 +0000

First let's compare the two so that you can make an informed decision. Both can be used to create GUI applications with Python.

That being said, PyQt has a lot of software available and a lot of learning resources. wxPython on the other hand seems more hobbyist, the amount of learning material is simply no match.

Programming methodology

PyQt and WxWidgets are both object oriented. That means you have to know about classes and objects when programming either one of them.

Because everything in Python is an object it makes sense to know object orientated programming.

Look and feel

wxPython uses the native toolkit on each operating system. This may cause some widgets to be available on one platform but not on the other.

PyQt uses the "Qt" style and you can change the style you use for your Qt applications.

Some of the available styles are (depending on your operating system):

'Breeze'
'Oxygen'
'QtCurve'
'Windows'
'Fusion'

GUI module

PyQt provides you with the concept of signals/slots that let you build your project as a set of components. WxPython on the other hand uses callbacks.

PyQt comes with a designer program that lets you build any desktop software. WxWidgets or wxPython on the other hand, has some third party designers but they don't match the amount of features PyQt has.

Why PyQt?

PyQt is not only a GUI library, it can do databases, networking and a lot more. At the same time, wxPython is only for GUI programming.

PyQt has a lot of example howtos and books, the amount of learning material is a lot larger for PyQt than wxPython.

If you are new to PyQt, I recommend this PyQt book.

Should I learn golang?

natamacm — Wed, 20 May 2020 18:24:06 +0000

Yes, it never hurts to learn a new language and Go is great at concurrency. Go (Golang) is an open-source programming language. It creates binaries from code and is not interpreted.

Go language is developed at Google and in syntax it's similar to C. But unlike C, it does memory management for you. It's great for building a back-end and is easy to deploy in the cloud.

The Go programming language has tools that let developers use memory in a secure way, collect garbage, manage objects, and allows them to type statically with concurrency.

So how to get started with Go?

For beginners, try the tutorial at golangr.com. It's a brief tutorial that goes over the basics.
Do the Go tour, which is like an interactive slide show. It also goes over the basics
Go through this book to learn more about Go
Go through some books like

Go in Action by William Kennedy, Brian Ketelsen, Erik St. Martin
Learning Functional Programming in Go by Lex Sheehan
The Go Programming Language by Alan A. A. Donovan and Brian W. Kernighan

There is no official Golang examination, but there are some companies offering training. These companies are not affiliated with Google.

File checksum

natamacm — Sat, 16 May 2020 18:45:05 +0000

A checksum is a sequence of numbers and letters used to check data for errors. You can generate a checksum for any file.

The generation of a checksum is called hashing and is done by a hashing algorithm.

You should know that hashing is not encryption. It just creates a hash, but it's impossible to reverse the process, unlike with encryption that requires a key to recreate the plain text.

You can get the checksum of any file in Python. There are several algorithms you can use. One of the older ones is md5. It's an older algorithm and I recommend newer ones. In fact md5 is from 1992 and it's better avoided.

To see a comparison of algorithms and attacks, check this page

You could use the sha256 algorithm to find a file checksum:

# Python program to find SHA256 hash string of a file
import hashlib

filename = input("Enter the input file name: ")
sha256_hash = hashlib.sha256()
with open(filename,"rb") as f:
    # Read and update hash string value in blocks of 4K
    for byte_block in iter(lambda: f.read(4096),b""):
        sha256_hash.update(byte_block)
    print(sha256_hash.hexdigest())

Hashlib has many implementations of hashing algorithms, you can see that in the Python shell:

>>> import hashlib
>>> hashlib.algorithms_available
{'sha256', 'blake2s', 'blake2b', 'sha384', 'md5', 'sha3_256', 'sha3_224', 'sha1', 'shake_256', 'sha3_512', 'shake_128', 'sha3_384', 'sha224', 'sha512'}

Detect any color with Python

natamacm — Wed, 13 May 2020 15:30:40 +0000

You can detect any color with Python. That can be a color of any object defined as string, like:

fish = WhatColorIsX.new('fish')

What it's doing behind the scenes is use Google Image API.

Installation

You can install the module WhatColorIsX with pip.

$ pip install WhatColorIsX

You may find you need to pip install Pillow as a dependency first, although it will be attempted automatically.

Import to your project

For almost all cases, call the new() factory function, then get the colour value from the color() method:

import WhatColorIsX

brick = WhatColorIsX.new('brick')
brick_color = brick.color()
fish = WhatColorIsX.new('fish')
fish_color_bright = fish.color(bright_hue=True)

If you already have PIL images that you want to process, you can use the same syntax:

from WhatColorIsX import whatcoloris_image
from PIL import Image

img = Image.open('images/cat.jpg')
cat = WhatColorIsX.new(img)
cat_color = cat.color()

Terminal image with Python

natamacm — Wed, 13 May 2020 15:26:35 +0000

You can display an image in terminal. Using Python you can use the module timg.

Setup

timg is available as a package on PyPI. You can install it with pip:

$ pip install timg

Now you can use the timg command in your terminal.

usage

To display an image from code:

import timg

obj = timg.Renderer()                                                                                               
obj.load_image_from_file("test.png")                                                                                
obj.resize(100,40)
obj.render(timg.ASCIIMethod)

That turns the image into ascii art.

To run it as command line program:

    usage: timg [-h] [-V] [-i] [-m METHOD] [-r N] [-s W] [filename]

    print an image in terminal


    positional arguments:
      filename              filename of an image

    optional arguments:
      -h, --help            show this help message and exit
      -V, --version         print version and exit
      -i, --invert-background
                            invert grayscale in ASCII mode
      -m METHOD, --method METHOD
                            name of a rendering method (use `-m list` to list
                            available methods, the default is a24h)
      -r N, --reduce-colors N

                            reduce color palette of an input image (1-256)
      -s W, --size W        width of an image