Modules and Packages in Python

As your program grows, you may want to split your code into multiple files for easier maintenance. Python allows you to do this using Modules and Packages.

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What is a Module?

A module is simply a file containing Python code (functions, classes, variables). You can use any Python file as a module by importing it into another file.

Example

Let’s say you have a file named mymodule.py:

def greeting(name):
    print(f"Hello, {name}!")

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

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Using the import Statement

To use a module, you use the import statement.

import mymodule

mymodule.greeting("Alice")
print(mymodule.person1["age"])

Renaming a Module

You can create an alias when you import a module by using the as keyword:

import mymodule as mx

mx.greeting("Alice")

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The from...import Statement

You can choose to import only parts from a module by using the from keyword.

from mymodule import person1

print(person1["country"])

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Built-in Modules

Python comes with a set of built-in modules, which you can import whenever you like.

import platform

x = platform.system()
print(x) # Output: e.g., 'Windows', 'Darwin', 'Linux'

Common built-in modules include: os, sys, math, random, datetime, and json.

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The dir() Function

The dir() function is a built-in function that lists all the function names (or variable names) in a module.

import math

print(dir(math))

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What is a Package?

A Package is a way of organizing related modules into a directory hierarchy. In simple terms, a package is a folder that contains multiple module files and a special file named __init__.py.

The __init__.py file can be empty, but it tells Python that this directory should be treated as a package.

Structure Example

my_package/
    ├── __init__.py
    ├── module1.py
    └── module2.py

To import from a package:

from my_package import module1