Python 24-Day Course - Day 10: Modules and Packages

Day 10: Modules and Packages

Importing Modules

import math
print(math.sqrt(16))   # 4.0
print(math.pi)         # 3.141592653589793

from random import randint, choice
print(randint(1, 100))
print(choice(["apple", "banana", "cherry"]))

Useful Standard Libraries

Module	Purpose	Example
`math`	Math functions	`math.ceil(3.2)`
`random`	Random number generation	`random.shuffle(lst)`
`os`	Operating system interface	`os.getcwd()`
`sys`	System parameters	`sys.argv`
`collections`	Specialized containers	`Counter, defaultdict`
`itertools`	Iterator tools	`product, permutations`

User-Defined Modules

You can create a utils.py file and use it as a module.

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

PI = 3.14159

# main.py
from utils import add, PI
print(add(3, 5))  # 8

name == “main”

# calculator.py
def multiply(a, b):
    return a * b

if __name__ == "__main__":
    # Runs only when executed directly
    result = multiply(3, 4)
    print(f"Result: {result}")

Package Structure

mypackage/
├── __init__.py
├── math_utils.py
└── string_utils.py

from mypackage.math_utils import add
from mypackage import string_utils

Today’s Exercises

Use collections.Counter to print the 3 most frequent characters in a string.
Use itertools.combinations to generate 5 lottery number combinations.
Separate calculator functions into a module and import them from a main file.