Importing Modules

A module is a file that contains Python code (functions, variables, classes) which can be reused in other programs.

Importing modules helps you:

• Reuse existing code
• Organize programs
• Use built-in libraries
• Save development time

WHAT IS A MODULE?

A module can be:

• A built-in Python module (like math)
• A user-defined Python file
• A third-party library

Example: math.py is a built-in module that provides mathematical functions.

1. BASIC IMPORT

import mathprint(math.sqrt(16))

Here, we import the math module and use sqrt().

Output:

4.0

2. IMPORT SPECIFIC FUNCTION

Instead of importing the whole module, you can import specific functions.

from math import sqrtprint(sqrt(25))

Now you don’t need to write math.sqrt().

3. IMPORT MULTIPLE ITEMS

from math import sqrt, piprint(sqrt(9))
print(pi)

4. USING ALIAS (AS)

You can rename a module using as.

import math as mprint(m.sqrt(36))

This is useful for long module names.

5. IMPORT ALL FUNCTIONS

from math import *print(sqrt(49))

⚠ Not recommended in large programs because it can cause name conflicts.

6. IMPORTING USER-DEFINED MODULE

Suppose you have a file named my_module.py:

def greet(name):
    return "Hello " + name

In another file:

import my_moduleprint(my_module.greet("Hira"))

Both files must be in the same folder.

7. COMMON BUILT-IN MODULES

• math → Mathematical functions
• random → Random numbers
• datetime → Date and time
• os → Operating system functions
• sys → System-specific parameters

Example:

import randomprint(random.randint(1, 10))

WHY IMPORT MODULES?

• Avoid rewriting code
• Keep code organized
• Use powerful built-in tools
• Build scalable applications

KEY TAKEAWAYS

• Use import module_name for full module
• Use from module import item for specific function
• Use as for alias
• Avoid import * in large projects

Importing modules is essential for writing efficient and professional Python programs.