Python Modules - Python Tutorial

Modules in Python are files containing Python code. This code can define functions, classes, and variables. A module is a way to structure your Python code and make it more manageable by dividing it into smaller, self-contained units.

Creating a Module

To create a module, you simply write your Python code in a file with a .py extension.

greet(name): This function takes a name and returns a greeting string.
add(a, b): This function takes two numbers and returns their sum.
pi: This is a constant representing the value of π.

# mymodule.py

def greet(name):
    return f"Hello, {name}!"

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

pi = 3.14159

Using a Module

To use a module, you need to import it into your Python script using the import statement.

import mymodule: This statement imports the module mymodule.
mymodule.greet("Alice"): Calls the greet function from mymodule with “Alice” as an argument.
mymodule.add(5, 3): Calls the add function from mymodule with 5 and 3 as arguments.
mymodule.pi: Accesses the pi variable from mymodule.

# main.py

import mymodule

# Using functions from the module
print(mymodule.greet("Alice"))  # Output: Hello, Alice!
print(mymodule.add(5, 3))       # Output: 8

# Accessing variables from the module
print(mymodule.pi)              # Output: 3.14159

Importing Specific Items

You can import specific functions, classes, or variables from a module using the from ... import ... statement.

from mymodule import greet, pi: Imports only the greet function and pi variable from mymodule.
greet("Bob"): Calls the greet function with “Bob” as an argument.
pi: Accesses the pi variable directly.

# main.py

from mymodule import greet, pi

# Using the imported function and variable
print(greet("Bob"))  # Output: Hello, Bob!
print(pi)            # Output: 3.14159

Using Aliases

You can assign an alias to a module or an item within a module to make it easier to reference.

import mymodule as mm: Imports mymodule and gives it the alias mm.
from mymodule import add as sum_up: Imports the add function from mymodule and gives it the alias sum_up.
mm.greet("Carol"): Calls the greet function from mymodule using the alias mm.
sum_up(10, 5): Calls the add function using the alias sum_up.

# main.py

import mymodule as mm
from mymodule import add as sum_up

# Using the module and function with aliases
print(mm.greet("Carol"))  # Output: Hello, Carol!
print(sum_up(10, 5))      # Output: 15

Exploring the `sys` Module

The sys module provides access to some variables and functions used or maintained by the Python interpreter.

import sys: Imports the built-in sys module.
sys.version: Retrieves the Python version.
sys.platform: Retrieves the platform on which Python is running.

import sys

print("Python version:", sys.version)
print("Platform:", sys.platform)

Python Modules Example Code

mymodule.py: Defines the module with a greeting function, an addition function, and a constant.
main.py: Imports the module and demonstrates using its functions and variables.

Step 1: Create a module named mymodule.py.

# mymodule.py

def greet(name):
    return f"Hello, {name}!"

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

pi = 3.14159

Step 2: Create a script named main.py that imports and uses the module.

# main.py

import mymodule

# Using functions from the module
print(mymodule.greet("Alice"))  # Output: Hello, Alice!
print(mymodule.add(5, 3))       # Output: 8

# Accessing variables from the module
print(mymodule.pi)              # Output: 3.14159