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Python

Python is an interpreted, object-oriented, high-level programming lanaguage with dynamic semnatics.

Usage: - Software development (e.g. Developing a website with the Flask library) - Data science (e.g. Creating a machine learning model with Tensorflow) - Automation (e.g. Creating a script to automate data analysis using Excel) Websites using python and django - Youtube - Instagram - Spotify - Dropbox - Pinterest

Naming Conventions

Class names should follow the CapWords convention.

For example: MyDog

Function names should be in all lowercase and underscores should be used to seperate words if necessary. 

def calculate_force(mass, acc):
    force = mass * acc
    return force

Indentation

  • Indentation groups lines of codes together. There should be 4 spaces per indentation. Spaces are preferred over tabs when making indentations.

  • You have to use the same number of spaces in the same block of code, otherwise Python will give you an error.

example: def calculate_force(mass, acc): force = mass * acc return force

Comments

There are blocks comments and inline comments.

Block comments are used when there are multiple lines of comments.

Inline comments should be used when we have a short comment that we would like to include within a line of code.

Or you can use multiline string literals because they are not assigned to a variable.

"""
This 
Is A
Multi-Line 
Comment
"""

Command Line

To run a program type the following: python version & python file name example: python myscript.py

Variables

We use variable to temporarily store data in computer's memory. - In python variables are created when you assign a value to it. - Python has NO command for declaring a variable. - Variables do not need to be declared with any particular type, and can even change type after they have been set.

Rules for python variables - A variable name must start with a letter or the underscore character - A variable name cannot start with a number - A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) - Variable names are case-sensitive (age, Age and AGE are three different variables) - A variable name cannot be any of the Python keywords. - Normally, when you create a variable inside a function, that variable is local, and can only be used inside that function. - To create a global variable inside a function, you can use the global keyword.

Example:

myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John"

Many Values to Multiple Variables Python allows you to assign values to multiple variables in one line. Many Values to Multiple Variables And you can assign the same value to multiple variables in one line.

Casting

If you want to specify the data type of a variable, this can be done with casting.

x = str(3) y = int(3) z = float(3)

Get the Type

You can get the data type of a variable with the type() function.

x = 5
y = "John"
print(type(x))
print(type(y))

Output

  • The best way to output multiple variables in the print() function is to separate them with commas, which even support different data

Practice

  • What is a correct syntax to add the value 'Hello World', to 3 variables in one statement? x = y = z = 'Hello World'
  • Insert the correct syntax to assign values to multiple variables in one line: x,y,z = "Orange", "Banana", "Cherry"

Python Collections (Arrays)

  • List is a collection which is ordered and changeable. Allows duplicate members.
  • Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
  • Set is a collection which is unordered, unchangeable*, and unindexed. No duplicate members.
  • Dictionary is a collection which is ordered** and changeable. No duplicate members.