Python Modules: Creation, Importing, and Advanced Usage

Python Modules

Discover how to build, import, and manage Python modules. Learn best practices, advanced import techniques, and module search paths.

Video: Python Modules

Watch an in‑depth tutorial on module fundamentals.

What Are Python Modules?

A module is simply a file containing Python statements and definitions. For example, example.py is a module named example. Modules help you break large programs into manageable, reusable pieces. Define common functions once and import them wherever needed.

Let’s create a small module. Save the following as example.py:

# example.py – a simple addition module

def add(a, b):
    """Return the sum of two numbers."""
    return a + b

How to Import Modules in Python

Use the import keyword to bring a module into the current namespace. For example:

>>> import example

Access its contents via the dot operator:

>>> example.add(4, 5.5)
9.5

Python ships with a rich standard library. You can browse all modules at Python Standard Library.

Python Import Statement

# Import the standard math module
import math
print("The value of pi is", math.pi)

The value of pi is 3.141592653589793

Import with Renaming

# Import math as a shorter alias
import math as m
print("The value of pi is", m.pi)

Renaming saves typing, but remember the original name (math) is no longer available.

Python from…import Statement

# Import only the constant pi
from math import pi
print("The value of pi is", pi)

Multiple names can be imported in one line:

from math import pi, e
print(pi, e)

Import All Names

from math import *
print("The value of pi is", pi)

Using * is discouraged because it pollutes the namespace and can obscure where a name came from.

Python Module Search Path

When Python imports a module, it checks:

• The current directory.
• Directories listed in the PYTHONPATH environment variable.
• Python’s installation‑specific default directories.

Inspect the path list with sys.path:

import sys
print(sys.path)
# ['', 'C:\Python33\Lib\idlelib', 'C:\Windows\system32\python33.zip', ...]

Reloading a Module

Modules are loaded only once per interpreter session. To re‑evaluate a changed module, use importlib.reload() (the imp module is deprecated in Python 3). Example:

# my_module.py
print("This code got executed")

>>> import my_module
This code got executed
>>> importlib.reload(my_module)
This code got executed

The dir() Built‑in Function

Use dir() to list all attributes of a module:

import example
print(dir(example))
# ['__builtins__', '__cached__', '__doc__', '__file__', '__name__', 'add']

Special attributes such as __name__ reveal module metadata:

print(example.__name__)
# 'example'

Calling dir() without arguments shows all names in the current namespace.