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Python

Is a popular programming lang

It was created by Guido van Rossum, and released in 1991

It is used for

web development(server-side)

software development

mathematics

system scripting

Good

It works on different platform(Windows, Mac, Linux, Rasberry Pi,…)

Was designed for readability, and has some similarities to the Eng with influence from math

Runs on an interpreter system, meaning that code can be executed as soon as it is written

Can be treated in a procedural way, an object-oriented way or a functional way

Know

The most recent major version of Python is Python3

However, Python2, although not being updated with anything other than security updates, is still quite popular

Install

Many PC will have python already installed

To check if you have python installed on Mac open the Terminal and type python --version

If do not have Python installed on computer, then can download it from www.python.org

Start

Write Python file called “helloworld.py”, which can be done in any text editor

print(“Hello, World!”)

Save file and open command line, navigate to the directory where file was saved, and run

~/Desktop python helloworld.py

The output should read

Hello, World!

Command Line

To test a short amount of code in python sometimes it is quickest and easiest not to write the code in a file

This is made possible because Python can be run as a command line itself

Type the following on Mac command line

~ > python

From there you can write any python code

Python 3.9.7 (default, Sep 16 2021, 08:50:36)
[Clang 10.0.0 ] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print(“Hello, World!”)	# Which will write “Hello, World!” in the command line
# Whenever you are done in the python command line, type the following to quit the python command line interface
exit()

Syntax

Execute

Python syntax can be executed by writing directly in the Command Line

Or by creating a python file on the server, using the .py file extension, and running it in the Command Line

Indentation

Refers to the spaces at the beginning of a code line

Where in other programming langs the indentation in code is for readability only, the indentation in Python is very important

Python uses indentation to indicate a block of code, Python will give an error if you skip the indentation

The number of spaces is up to programmer, but it has to be at least one

Have to use the same number of spaces in the same block of code, otherwise Python will give an error

Variables

Are created when you assign a value to it

x = 5
y = “Hello, World!”

Python has no command for declaring a var

Comments

Can be used to explain Python code

Can be used to make the code more readable

Can be used to prevent execution when testing code

# This is a comment, it starts with a “#”, and Python will ignore them
print(“Hello, World!”) # Comments can be placed at the end of a line, and Python will ignore the rest of the line

Python does not really have a syntax for multi line comments

But, not quite as intended, can use a multiline string

“””
Since Python will ignore string literals that aren’t assigned to a var,
you can add a multiline string(triple quotes) in your code, and place your comment inside it
”””