Modules & Packages

A module is simply a Python file ending in `.py`. You can define functions, classes, and variables in a module and `import` them into other files to reuse code.

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

# main.py
import math_utils
print(math_utils.add(5, 3))

You can import an entire module, specific items, or give them aliases. Choose the style that makes your code most readable.

Python
import math
from math import sqrt
import numpy as np

print(math.pi)
print(sqrt(16))
# print(np.array([1, 2]))

A package is a directory containing multiple module files. It must (usually) contain a special file named `__init__.py`, which can be empty or used to expose specific functions.

Python
my_project/
├── main.py
└── graphics/
    ├── __init__.py
    ├── shapes.py
    └── colors.py

# main.py
from graphics import shapes

A virtual environment is a self-contained directory that contains a Python installation for a specific project. This prevents version conflicts between different projects.

Python
# Terminal commands
python -m venv venv       # Create
source venv/bin/activate  # Activate (Mac/Linux)
.\venv\Scripts\activate   # Activate (Windows)
pip install requests      # Install packages safely