Forem: bluepaperbirds

multiple assignment in Python

bluepaperbirds — Wed, 13 Jan 2021 23:51:14 +0000

hey people what's going on? hope you're doing well.

i'm going to explain multiple assignment in python, so sit back relax and enjoy the article.

multiple assignment allows us to assign multiple variables at the same time using one line of code.

here's an example of us using standard assignment. let's say we have a variable name and i will set this to a value of my name.

name = "Tux"
print(name)

let's say edge equals 21 and how about a variable called attractive?

name = "Tux"
edge = 21
attractive = True

i think i'm gonna set this to true okay, so we have a bunch of variables and then we can print the value of these variables with some print statements.

print(name)
print(edge)
print(attractive)

so let's print name age and attractive. so we have name age attractive and as you would expect this prints tux 21 and true.

now another way in which we could write the same code is to use multiple assignment and this allows usto assign multiple variables at the same time using one line of code.

so i'm going to turn all of these lines into comments and this time we will only use one line of code.

# name = "Tux"
# edge = 21
# attractive = True

But to do this we're going to list all of our variables separated with a comma so that would be name comma edge comma attractive.

We will set them equal to those values but in the same order separated by commas so that would be tux comma 21 comma true and this would do the same thing, only using one line of code.

name, edge, attractive = "Tux", 21, True

You can print the variables on one line too

>>> name,edge,at = "Tux",21,True
>>> print(name, edge, at)
Tux 21 True
>>>

If you have a large program or use loops/if statements keep in mind the variable scope

Get all keys and values from json object in Python

bluepaperbirds — Tue, 12 Jan 2021 16:39:58 +0000

In this Python tutorial we are going to see how we can get all the keys in this json object and also all the values of the keys.

okay so let me get started let me take one empty python file
here, so yeah so let me save this file first as example.py.

Load json

As it is a json i need to import this package called json. This lets you play around with json. Then it is available in this particular Python file.

import json

Right so take that file path and try to open that with open as json file.

with open("C:\\pythonPrograms\\example.json") as jsonFile:

That will do json decoding. Our json file looks like this:



    {"emp_details":[
             {"name": "a",
              "id": "123"
             },
             {"name":"b",
              "id":"345"
             }
    ]
    }

You need to give the file name, so this is my file name. It should have double slashes not the single slash, so once we have this using the json library that we have imported you need to load the json object. Let's go.

Get keys and values

Using load function json file, this let me keep it into a variable called data.



    data = json.load(jsonFile)

Then you have a Python object. Now you can get the keys and values. The code below depends on what your json file looks like. In our json file there's a header named emp_details.



    jsonData = data["emp_details"]
    keys = x.keys()
    values = x.values()

That gives us this code:



    import json

    with open("test.json") as jsonFile:
        data = json.load(jsonFile)
        jsonData = data["emp_details"]
        for x in jsonData:
            keys = x.keys()
            print(keys)
            values = x.values()
            print(values)

It will output:

{'name': 'a', 'id': '123'}
dict_keys(['name', 'id'])
dict_values(['a', '123'])
{'name': 'b', 'id': '345'} 
dict_keys(['name', 'id'])
dict_values(['b', '345'])

If you want, you can loop over the keys and values inside the loop, to do the formatting.

Here we use a for loop to iterate over the keys and values. If your json file is small like the one in this example, you don't necessarily have to use a loop.

That's all :-)

Python vs Go

bluepaperbirds — Tue, 12 Jan 2021 14:07:04 +0000

what's the difference between the Python programming language and the Go programming language and which should
you choose?

Speed

Okay sorry there are different areas the first area is speed. So go is based on C++ so it's really fast, it's as fast as C++.

Python is a bit slower so if you rely on speed then you should take go. Go is compiled
programming language. It is a traditional programming language that is compiled down and then executed in bytecode.

The Python programming language which is interpreted so you can quickly try things out so if you want to get paid highly then I recommend a Python.

In the US, you will get six figures easily.

Concurrency

Go is a much younger language released in 2009, Python in 1991 so python is still the 800-pound gorilla with much more experience regarding object orientation.

Go is not object orientated and Python is object oriented, so it's more useful abstraction in many cases python has like concurrent libraries which execute concurrently.

If you rely on parallel programming and distributed things then go is much easier it has built-in concurrency support.

Python does not but you can import it easily with the library. So in memory management Python doesn't let you to customize memory management, so it is like automatic in go.

Go has some customization features so it's a bit more powerful in memory management for the user.

General purpose?

For the programmer, Python is much more popular. It is a really simple programming languages to learn, ok so how does go look?

print("hello world")

Go uses parenthesis and it's different, like a bit like the C++ language with some Python language add-ons.

package main

import "fmt"

func main() {
   fmt.Println("Hello, World!")
}

Ok so Go feels like an intermediate between Python and C++. Python yeah it looks very clean there are no parentheses and brackets and so on so it's a bit easier to read I would say. It is easier to write and it's a bit cleaner. For a beginner, I'd say Go is harder to learn.

The Python programming language dominates for general purpose programming. You can use it for gui programming, web development, machine learning and lots of other things.

Go can be used in many domains, but it's not matured yet in all those domains and lots of software is written in Python.

Python assign functions and memory address

bluepaperbirds — Tue, 12 Jan 2021 13:09:52 +0000

Hello what's going on everybody?

I'm going to show you guys how we can assign a function to a variable in Python. I will show you all how we can assign a function to a variable.

Now let's say we have a function named hello and all we'll do is print the word hello.

You know to call this function, you would type the name of the function followed by a set of parentheses.

hello()

and this will print the word "hello" the set of parentheses that comes after a function's name is the portion that will call the function. If you were to remove that set of parentheses afterwards we would not in fact call that function.

For simplicity, we'll leave out the main function from these examples.

Function memory address?

Now with python python will pretty much treat everything as objects including functions. So there's something i want to show you guys, if i was to print the name of my function hello what will be displayed is the memory address of this function.

>>> def hello():
...     print("hello")
... 
>>> hello
<function hello at 0x7f21d6d4e3a0>
>>>

This is the memory address of where this function is located within my computer's memory and it's in hexadecimal think of it like a street address such as 123 fake street. This is the address of where this function is within my computer's memory and each time that i run this program this number can change as you can see it here.

Now one thing that we could do we could assign this address to a variable let's say hi equals hello and be sure that you're not adding that set of parentheses afterwards because then you would be calling the hello function and returning the result to hi.

>>> hi = hello
>>> hi
<function hello at 0x7f21d6d4e3a0>
>>>

So hi equals hello no parentheses and if i was to print hi well the address of hello and hi will be at the same memory address both of these numbers are the same now.

The above function is using a single return but this works with multiple return too. So what it will return are two memory addresses.

>>> def hello():
...    print('hello')
... 
>>> def time():
...    print('14:00')
... 
>>> hi,t = hello, time
>>> hi
<function hello at 0x7f3db682f3a0>
>>> t
<function time at 0x7f3db682f430>
>>>

Call function

What do you imagine would happen if i was to call the hi function after we assign the memory address of hello to hi well then what we'll end up doing is calling the hello function.

>>> hi()
hello
>>>

Even though we're listing that we would like to call the hi function even though it doesn't exist so it's as if this hello function has two names you, can either use hello or you can use hi. That's because we're assigning the
memory address of hello to this variable of hi, so we could treat hi as a function.

It's kind of like an alias where this function has two names.

What 's the Golang developer salary in Germany?

bluepaperbirds — Sun, 10 Jan 2021 12:52:05 +0000

In Berlin, Germany there are tech companies with golang jobs.

So what is the average annual salary you can expect?

It is seventy thousand three hundred seventy five euros (73.175 euros or $89.427). That is gross so before tax the salary range for golang engineers in Berlin Germany is from 65000 euros per year up to 73175 euros per year.

This is gross before tax!

Now the weather you fall on the lower range of that scale or the upper range of that scale well depends on a number of factors.

How to get the higher paid job?

I find that the two most important ones are your seniority (something you can't really change) and the financial situation that the company is in (pick the company wisely)

Your seniority will also depend on a number of factors like the years of experience working as a full-time developer is one thing and you need to have minimum three years of full-time experience to be considered the mid-level in Berlin.

If you are new to Golang, there's a good tutorial here.

How to get a Golang job?

But many companies don't just look at the years of experience some actually look much deeper into the complexity of the systems that you have developed in the past as well as at your ability to write reliable code code that scales and code that is clean.

The financial situation of the company always depends on a number of factors but the basic ones include is it a privately owned company does it have investors is it an international corporation with headquarters in Berlin or or just Berlin office.

Am I eligable?

It's fine if you speak only English, German companies
don't usually require German for their engineering jobs. When you're looking at salaries in Berlin Germany keep in mind that the numbers I shared with you is the base salary so around 60, 70 thousand euros per year.

If you are from outside of the European Union you will need either a blue card or a regular work permit to start a job in Berlin.

10 things about the Ruby programming language

bluepaperbirds — Sun, 10 Jan 2021 12:38:00 +0000

Ruby is an interpreted, high level, general purpose language.It supports different paradigms like functional procedural and object-oriented.

From the official website, it is stated that Ruby is, "a dynamic, open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write." Ruby on Rails on the other hand is a full stack web development framework.

Packages (programs and libraries) are referred to as gems in Ruby. RubyGems is a package manager for Ruby.Some implementations include GoRuby, Topaz, Opal, mruby and JRuby.

I would like to share this quote from the creator of the language. He built a language to suit his needs and this was part of it.

Ruby is a pure object oriented language. Everything is an object. Even a class is an object.

Some programming constructs that are supported by Ruby include mixin, open classes, meta programming, duck typing, YAML, automatic returns.

Features of Ruby lend itself to high quality coding.The redo keyword caught my attention as interesting. Redo, next and retry can be used to control loops.

Finally, I would like to share this useful tutorial I found

What's vue.js?

bluepaperbirds — Sun, 10 Jan 2021 12:24:48 +0000

Vue.js it's a JavaScript framework for building front-end UIs. In Vue.JS you can start simple and then progressively add in the tools and features that you need to build a complex web application.

At its core it provides a way to build components that encapsulate data or state in your JavaScript and then connect that state reactively to a template in HTML.

We call these components declarative views because the same data inputs will always produce the same output in the visual UI.

How does it work?

When we declare data on this data object it links or binds it to the HTML on the template above when the value of the data changes the component will automatically rerender. In other words it's reactive and the framework does a ton of work under the hood to make sure that this process is performance across a huge component tree we can work with this data in the template thanks to views HTML based template syntax we can interpolate a value for expression using double braces and we also have a variety of directives to control the behavior of the HTML based on the data.

We can use Vue.js to only render an element when the value is True and then we might have a fallback element after that that's only rendered.

We can do that directly in the template or define a custom method and the components methods object the method has access to our reactive data and that
means all we have to do is change the value of the data and the component will automatically rerender and that's all it takes to build an interactive reactive declarative UI component with Vue.js.

You can see vue.js examples here.

Who uses Vue.js?

The framework is loved by developers for the simplicity but also its ability to scale up in complexity incrementally its plugin system allows you to easily drop in things like a router state management firebase support and more and perhaps
best of all it's not sponsored by some mega corporation.

It's not pressured to push out new releases all the time and does a great job listening to its community.

Start an external program with Python

bluepaperbirds — Sun, 10 Jan 2021 10:49:43 +0000

You can start a program using just Python code. You do so by a module called subprocess.

If it is a terminal program, you can save its output in your Python program.

#!/usr/bin/env python

from subprocess import Popen, PIPE

process = Popen(['cat', 'test.py'], stdout=PIPE, stderr=PIPE)
stdout, stderr = process.communicate()
print(stdout)

The cat command outputs the contents of a file on a Linux system. This may also work on Mac, but if you're on Windows try another command.

You can start non-terminal programs. This works for any program regardless of if it's something simple like notepad or something more advanced like chrome.

On Linux there's the program mousepad, which is a clone of the notepad program. You could run it like this:

>>> import subprocess
>>> import sys
>>> result = subprocess.run(["mousepad"])

The subprocess module lets you do all kinds of things with running programs.

This module is part of the standard modules, so you don't have to install it with the Python package manager.

If the program is taking to long to execute, you can use a timeout

import subprocess
import sys

result = subprocess.run([sys.executable, "-c", "import time; time.sleep(3)"], timeout=1)

Ruby on OpenBSD

bluepaperbirds — Sat, 09 Jan 2021 18:10:16 +0000

If you use OpenBSD for security reasons, you can use several versions of Ruby. OpenBSD is a unix system that has many built-in security mitigations.

Install Ruby

You can use the command pkg_info to get information on packages

doas pkg_info -Q ruby

This returns all related ruby packages. On the latest OpenBSD version. To check your OpenBSD version

$ uname -a
OpenBSD foo.home 6.8 GENERIC.MP#2 amd64

In my version it returns

jruby-9.2.13.0
mruby-2.0.1p0
ruby-2.5.8p0
ruby-2.6.6p0
ruby-2.7.1p1

This is the default OpenBSD packages, not the ports repository. In the ports repository, they didn't do a security audit on the software packages.

You can install ruby with the command

doas pkg_add ruby-2.7.1p1

If you are new to Ruby, try this Ruby tutorial.

Then to run program you can use ruby27.

ruby27 program.rb

Of course Ruby isn't the only programming language you can use on Go. There's C, C++, Golang, Python, PHP and a lot more.

Interactive websites with vue.js

bluepaperbirds — Sat, 09 Jan 2021 17:46:35 +0000

JavaScript isn't going anywhere soon, and these days JavaScript is used to make all kinds of things including Web Apps. Who would have thought that the web browser became a kind of operating system?

What is Vue.js?

Vue.JS is javascript framework that inspired by Angular. You can find some Vue examples here.

If you have a single page web page, you can make it interactive using Vue.js.

You can make all kind of on page interacts with Vue and even small apps that don't require a back-end. In fact one of the things you can do is interact with an API and present the data on a single page (as an app) with Vue.js.

Pretty cool right? or do you prefer React or another framework when working with the web?

Why Vue.js?

There are several reasons why you could use vue.js

First it's approachable. If you already know HTML, CSS and JavaScript you can build things in no time!

It's scalable and it has a small footprint which is important for page speed. It has a 20KB min+gzip Runtime

Watermark pdf

bluepaperbirds — Sat, 09 Jan 2021 16:19:27 +0000

You can do a lot of neat things using the Python programming language. Using Python you can easily watermark a pdf. You can use a module called python3-fitz which uses MuPDF underneath (install this too)

If you don't know the Python programming language, I recommend this tutorial as a starting point.

You can install both fitz and mupdf using your package manager.

sudo apt install python3-fitz
sudo apt install mupdf

Python watermark

Then you need an input file and an image. Set the position using the fitz.Rect() function.

Load the module like this:

import fitz

Install it using your operating systems package manager. If you use pip, there seem to be some other packages named fitz which are conflicting.

Then open the pdf

doc = fitz.open("input.pdf")

Set the location of your watermark

rect = fitz.Rect(0, 0, 100, 100)

Iterate over the pages and insert the water mark

for page in doc:
    page.insertImage(rect, filename="logo.jpeg")

And save it. The full code:

import fitz
doc = fitz.open("input.pdf")
rect = fitz.Rect(0, 0, 100, 100)

for page in doc:
    page.insertImage(rect, filename="logo.jpeg")

doc.save("output.pdf")

If you run the program it will output a new pdf with the watermark image on top of every page.

Make a backup of your file before you run it. If you want, you can build a GUI around it using something like tkinter or pyqt

try-catch

bluepaperbirds — Thu, 27 Feb 2020 13:30:39 +0000

Errors can happen if a Python program is running. There are many types of errors, like a "couldn't open file error" or "zero division error".

If an error pops up, that doesn't mean your program should crash.

So how do you stop it from crashing?

You can use the try-except code. Other programming languages like C# or Java call this the try-catch block.

You can use this to catch errors (sounds better than to except). Some code examples listed below:

try:
    for i in range(5):
        print(5/i)
except:
    print("Zero division")

print("End program")

For opening a file, where the filename is given as user input:

>>> filename = input("Enter file:")
Enter file:test.txt
>>> try:
...     with open(filename) as f:
...         lines = f.read()
... except:
...     print("Couldn't open file")
... 
Couldn't open file
>>>

Doing some maths, catch different types of exceptions:

a,b=1,0
try:
    print(a/b)
    print('10'+10)
except TypeError:
    print("Cannot add, values are incompatible data types")
except ZeroDivisionError:
    print("Divided by zero")

You can apply this for function calls too, or inside functions.

try:
    start()
    accel()
    turn()
except:
    print("Car error")