Here’s a simple explanation of Libraries and Packages in Python — with examples, usage, and practice questions

📚 What is a Library in Python?

• A library is a collection of useful code (functions, classes, modules).
• It helps you do things quickly, without writing code from scratch.
• Python has many libraries for math, data, web, AI, etc.

🔹 Examples of Libraries:

📦 What is a Package?

• A package is a folder that contains modules (Python files) and a special file called __init__.py.
• Packages help to organize libraries better.
• You can think of:
  • Library = a toolset
  • Package = toolbox with organized tools (modules)

✅ Example: Using a Library

1. Math Library:

import math
print(math.pi)         # 3.1415...
print(math.sqrt(25))   # 5.0

2. Random Library:

import random
print(random.randint(1, 10))  # Random number between 1 and 10

✅ Using an External Library

• Some libraries are not built-in. You need to install them using pip:

pip install pandas

Then use it:

import pandas as pd
data = pd.Series([1, 2, 3])
print(data)

✅ Example: Package Structure

Imagine this folder:

mypackage/
    __init__.py
    add.py
    sub.py

add.py

def add(x, y):
    return x + y

sub.py

def sub(x, y):
    return x - y

Use the Package:

from mypackage import add, sub
print(add.add(3, 2))
print(sub.sub(5, 2))

📝 Practice Questions + Answers

❓ Q1: What is the difference between a module and a library?

✅ Answer:

• A module is one Python file (.py) with code.
• A library is a collection of modules.
• A package is a folder containing modules.

❓ Q2: Use the random library to generate a number between 100 and 200.

✅ Code:

import random
print(random.randint(100, 200))

❓ Q3: Install and use the numpy library to create a number array.

✅ Code:

pip install numpy

✅ Python:

import numpy as np
arr = np.array([10, 20, 30])
print(arr)

❓ Q4: What is the role of __init__.py in a package?

✅ Answer:

• It tells Python that the folder is a package.
• It can be empty or contain startup code.

❓ Q5: Create your own library with a function to find the square of a number.

✅ Create mylib.py:

def square(n):
    return n * n

✅ Use it:

import mylib
print(mylib.square(6))  # Output: 36

🔄 Summary Table