Modules and Packages

What is a Module?

A module is a Python file full of ready-made code (functions, variables) that you can reuse. Instead of writing everything yourself, you import a module and use its tools. A package is a folder of related modules.

Ways to Import

import math               # import the whole module
print(math.sqrt(16))

from math import pi       # import one name
print(pi)

import math as m          # give it a short alias
print(m.factorial(5))

• import math → use as math.sqrt.
• from math import pi → use pi directly.
• import math as m → short alias m.

Useful Built-in Modules

Program 1: Using math

import math
print("Square root of 25 :", math.sqrt(25))
print("5 factorial       :", math.factorial(5))
print("Value of pi       :", round(math.pi, 4))
print("2 to power 10     :", math.pow(2, 10))

Program 2: Using random

import random
print("Random 1-6  :", random.randint(1, 6))   # dice roll
fruits = ["apple", "mango", "kiwi"]
print("Random fruit:", random.choice(fruits))
random.shuffle(fruits)
print("Shuffled    :", fruits)

randint gives a whole number in a range; choice picks one item; shuffle mixes a list. (Output changes each run.)

Program 3: Your Own Module

Any .py file can be your own module. Create mytools.py:

def add(a, b):
    return a + b

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

Then use it in another file:

import mytools
print(mytools.add(5, 3))
print(mytools.greet("Aman"))

Packages & pip

A package is a folder of modules. Many packages are not built in — you install them with pip, Python's package installer.

pip install numpy
pip install pandas

After installing, import numpy and use it like any module.

Common Mistakes

• Naming your file the same as a real module (e.g. random.py) — it confuses imports.
• Forgetting to install a package with pip before importing.
• Expecting random output to be the same every run.

Practice Tasks

1. Use math to find the area of a circle (pi r squared).
2. Use random to simulate rolling two dice and print the sum.
3. Make a module with two functions and import it into another file.
4. Use the statistics module to find the mean of a list.

Summary

• A module is a reusable Python file; a package is a folder of modules.
• Import with import, from ... import, or import ... as.
• Built-in: math, random, datetime, os, statistics.
• Install extra packages with pip install.