Python Modules

Python modules are .py files that consist of Python code. Any Python file can be referenced as a module.

Some modules are available through the Python Standard Library and are therefore installed with your Python installation. Others can be installed with Python’s package manager pip. Additionally, you can create your own Python modules since modules are comprised of Python .py files.

Writing and Importing Modules

Writing Modules

Writing a module is just like writing any other Python file. Modules can contain definitions of functions, classes, and variables that can then be utilized in other Python programs.

From our Python 3 local programming environment or server-based programming environment, let’s start by creating a file hello.py that we’ll later import into another file.

To begin, we’ll create a function that prints Hello, World!:

# math_operations.py (Located under my-own-modules directory)

# Maths Operation

def add(a, b):
    print(a + b)

If we run the program on the command line with python math_operations.py nothing will happen since we have not invoked the functions add.

Importing Modules

Let’s create a second file called main_program.py so that we can import the module we just created, and then call the function.

main_program.py
# Import math_operations module - which is nothing but the math_operations.py file
import math_operations


# Call function
math_operation.add(1, 2)

Because we are importing a module, we need to call the function by referencing the module name in DOT " . " notation.

We could instead import the module as from hello import world and call the function directly as world(). You can learn more about this method by reading how to using from … import when importing modules.

Python Functions

Python functions are written inside .py files which performs the instruction or action written in Python. each method/function performs set of instruction or operations we wanted to perform. like adding two numbers, checking if the user is admin or not etc.,

Creating Function

In order to create python functions/methods you need to use def key word prefixed. lets see the below example.

# functions.py
# def -> key word tells us this is a method.
# display_app_name(): this is our method name with no parameters, because with in the brackets we have not passes any variable.
def display_app_name():
    print("My App Name")

Calling Function

Calling a medhod in Python is easy, just need to use the method name with the brackets. (If method has any parameters, we need to just pass it inside the brackets.)

# calling the function
display_app_name()

Returning data from Function

# functions.py
def get_current_username(user):
    return user["name"]

userobj = {
    "name": "John",
    "id": 100}

print(get_current_username(userobj))

Calling function inside another function.

# functions.py
def is_admin(user_param):
    return user_param["admin"]

def append_usertype(old_user_id, user_type):
    return f"{old_user_id}_{user_type}"


def regenerate_userid(user_param):
    new_userid = user_param["id"]
    if is_admin(user_param):
        new_userid = append_usertype(new_userid,"ADM")
    else:
        new_userid = append_usertype(new_userid,"USR")

    user_param["id"] = new_userid
    return user_param

#-----------------------------------------

user = {
    "name": "John",
    "id": 100,
    "admin": False
}
print(user)
print(regenerate_userid(user))