What Is a Python Module?

In Python programming, a module functions as a reusable code library. Essentially, it is a file that contains a collection of functions, variables, and classes designed to be included in your application to extend its capabilities.

How to Create a Python Module

Creating a module is straightforward: simply save your Python code within a file that uses the .py extension. This file then becomes a module that you can import into other Python scripts.

# Example: Save this code in a file named mymodule.py
def greeting(name):
    print("Hello, " + name)
    

Using a Python Module

After creating a module, you can access its functions or variables by importing it using the import statement. For example:

import mymodule

mymodule.greeting("Jonathan")
    

Note that when calling a function from a module, the syntax follows the pattern module_name.function_name().

Variables Within a Module

Modules are not limited to functions; they can also contain variables of various types such as dictionaries, lists, and objects.

# Example: Define a dictionary in mymodule.py
person1 = {
    "name": "John",
    "age": 36,
    "country": "Norway"
}
    

Accessing this dictionary after importing the module:

import mymodule

age = mymodule.person1["age"]
print(age)
    

Naming and Renaming Modules

Modules must be saved with a .py extension but the filename itself can be anything meaningful to your project. Furthermore, when importing a module, you may assign it an alias using the as keyword to simplify references:

import mymodule as mx

age = mx.person1["age"]
print(age)
    

Exploring Python’s Built-in Modules

Python offers numerous built-in modules that provide additional functionality. For example, the platform module lets you retrieve information about the operating system:

import platform

os_name = platform.system()
print(os_name)
    

Listing Module Contents with dir()

To inspect all functions and variables defined within a module, use the built-in dir() function:

import platform

contents = dir(platform)
print(contents)
    

This method is applicable to all modules, including those you create yourself.

Selective Import Using from Keyword

If you only need specific components from a module, the from statement allows selective importing:

# In mymodule.py
def greeting(name):
    print("Hello, " + name)

person1 = {
    "name": "John",
    "age": 36,
    "country": "Norway"
}

# In your main script
from mymodule import person1

print(person1["age"])
    

When using selective import, you can directly reference the imported elements without prefixing them with the module name.