Learn What Modules Are in Python: Absolute Beginners Tutorial

A module in Python is a file containing reusable code. Once you understand modules, you can stop rewriting the same functions over and over — and start pulling in thousands of ready-made tools that ship with Python itself.

When you start writing Python, everything goes into one file. That works fine for short scripts. As programs grow, though, a single file becomes hard to navigate and maintain. Modules solve this by letting you split code into separate files, then load what you need on demand. Python has used this system since its earliest versions, and the entire ecosystem — from the standard library to third-party packages — is built on top of it.

What Is a Module?

A module is a plain Python file with a .py extension. That is the entire definition. Any file you write — greetings.py, calculator.py, utils.py — is already a module. When another Python script imports that file, Python runs the file, stores its names (functions, classes, variables), and makes them available through a module object.

The module object acts like a container. Every name defined inside the file is an attribute of that container. You reach those attributes through dot notation: module.name.

Creating your first module

Suppose you save the following code in a file named greetings.py:

# greetings.py

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

def say_goodbye(name):
    return f"Goodbye, {name}. See you next time."

DEFAULT_GREETING = "Hi there!"

In another file in the same directory, you can load everything from greetings.py with a single line:

# main.py
import greetings

print(greetings.say_hello("Jordan"))
# Output: Hello, Jordan!

print(greetings.DEFAULT_GREETING)
# Output: Hi there!

The __name__ attribute

Every module has a built-in attribute called __name__. When you run a file directly from the terminal, Python sets __name__ to the string '__main__'. When the same file is imported by another script, Python sets __name__ to the module's filename (without the .py extension). This lets you write code that behaves differently depending on how the file is used:

# greetings.py

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

if __name__ == "__main__":
    # This block only runs when you execute greetings.py directly.
    # It does NOT run when greetings is imported elsewhere.
    print(say_hello("World"))

Importing Modules: Three Ways to Do It

Python gives you several import styles. Each one puts names into your script's namespace differently. Choosing the right style affects readability and whether name collisions can occur.

Style 1 — import module_name

The simplest form. The entire module loads and is accessible through its name.

import math

result = math.sqrt(49)   # 7.0
pi_value = math.pi       # 3.141592653589793

print(result)
print(pi_value)

Style 2 — from module_name import name

Imports only one specific name. That name lands directly in your local namespace, so you skip the module prefix.

from math import sqrt, pi

result = sqrt(49)    # No math. prefix needed
print(pi)            # 3.141592653589793

Style 3 — import module_name as alias

Gives the module a shorter or more convenient name. This is common in data science and scientific computing communities.

import random as rng

number = rng.randint(1, 100)
print(number)    # A random integer between 1 and 100

The table below summarizes the three approaches side by side:

The Python Standard Library

Python ships with a large collection of ready-to-use modules called the standard library. No installation is needed — every module in it is available the moment Python is installed on a machine. The official documentation describes it as offering a wide range of facilities for working with the operating system, networking, data formats, mathematics, and more.

The table below highlights some frequently used standard library modules that beginners encounter early:

Here is a short example that uses three standard library modules together:

import math
import random
import datetime

# Pick a random number and compute its square root
number = random.randint(1, 100)
root   = math.sqrt(number)

# Get today's date
today  = datetime.date.today()

print(f"Date: {today}")
print(f"Random number: {number}")
print(f"Square root: {root:.4f}")

Python Learning Summary Points

1. A module is any .py file. Its functions, classes, and variables become attributes of a module object that you access with dot notation after importing.
2. Python provides three main import styles: import module, from module import name, and import module as alias. The first is the safest choice for beginners because it keeps names organized inside their module's namespace.
3. The standard library ships with Python and requires no installation. Start with math, random, os, datetime, and json — these cover a wide range of common tasks and appear frequently in beginner-to-intermediate Python code.
4. The if __name__ == "__main__": guard prevents code from running automatically when a file is imported. Use it to separate a module's reusable code from test or demonstration logic.
5. Namespaces protect your code from accidental name collisions. Every module has its own namespace, and import module keeps that namespace separate from your script's globals.

Modules are the foundation of every Python project beyond a single script. Once you are comfortable with the import system, the entire standard library — and the thousands of third-party packages available through pip — becomes accessible to your programs.