📦 Modules & Packages

Code Organization & Reusability

Python Modules

Modules are Python files containing code that can be imported and reused. They help organize large projects and share code across files.

💻 Importing Modules

# Import entire module
import math
print(math.sqrt(16))  # 4.0
print(math.pi)        # 3.14159...

# Import specific items
from math import sqrt, pi
print(sqrt(25))  # 5.0
print(pi)

# Import with alias
import numpy as np
import pandas as pd

# Import everything (not recommended)
from math import *

📝 Creating Modules

# mymath.py
def add(a, b):
    return a + b

def multiply(a, b):
    return a * b

PI = 3.14159

# main.py
import mymath

result = mymath.add(5, 3)
print(result)  # 8
print(mymath.PI)  # 3.14159

🎯 Key Takeaways

import: Use external code
from...import: Import specific items
as: Create module aliases
__name__: Check if module is main program
pip: Package installer for Python
Standard library: Built-in modules (os, sys, datetime)