[Leejohnston]

Chapter 15 — Modules & Importing Code
Modules are collections of functions, tools, and features that you can bring into your program with a single command.

Python becomes extremely powerful the moment you begin importing modules.

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15.1 What Is a Module?

A module is a file that contains:

• functions 
• variables 
• tools 
• classes 

You import it to use those features.

Examples of built-in modules:

• math 
• random 
• time 
• statistics 
• os 

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15.2 Importing a Module

Basic import:

Code:

import math

Then use it:

Code:

print(math.sqrt(25))

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15.3 Importing Specific Functions

Code:

from math import sqrt, pi

print(sqrt(49))
print(pi)

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15.4 Renaming a Module (Alias)

Useful for long module names:

Code:

import statistics as stats

print(stats.mean([2, 4, 6]))

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15.5 The math Module

Common tools:

Code:

math.sqrt(x)
math.floor(x)
math.ceil(x)
math.pi
math.e

Example:

Code:

import math
print(math.floor(3.9))  # 3

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15.6 The random Module

Generate randomness:

Code:

import random

print(random.randint(1, 6))  # random dice roll
print(random.choice(["red", "blue", "green"]))

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15.7 The time Module

Delay programs:

Code:

import time

print("3...")
time.sleep(1)
print("2...")
time.sleep(1)
print("1...")

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15.8 Writing Your Own Module

Create a file: 
mymath.py

Put this inside:

Code:

def triple(x):
    return x * 3

Then import in another file:

Code:

import mymath

print(mymath.triple(5))

You just created a module.

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15.9 Importing Everything (Use Carefully)

Code:

from math import *

This gives access to all math tools directly:

Code:

print(sqrt(81))

But this can cause naming conflicts. Use sparingly.

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15.10 Real-World Use — JSON Module

APIs send data in JSON format.

Code:

import json

data = '{"name": "Lee", "score": 95}'
parsed = json.loads(data)
print(parsed["name"])

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15.11 Mini Project — Random Password Generator

Use random.choice() to create a password with:

• letters 
• numbers 
• symbols 

Length: 10–15 characters.

Example output:

Code:

Your password: 7G!pK3a@2m

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15.12 Challenge — Dice Battle Simulator

Rules:

• two players roll dice (1–6) 
• use random.randint() 
• highest number wins 
• repeat 5 rounds 
• show total wins 

Example:

Code:

Round 1: Player A wins
Round 2: Tie
Round 3: Player B wins
...

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15.13 Chapter Summary

• modules add extra abilities to Python 
• import the whole module or specific functions 
• math, random, time, and json are essential tools 
• you can write your own modules 
• modules make programs cleaner, shorter, and more powerful 

Next:
Chapter 16 — File Handling: Reading & Writing Data

This is when learners start interacting with real files — saving data, loading data, and building real software.

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Written and Compiled by Lee Johnston — Founder of The Lumin Archive