Python Modules

On This Page

• 12.1  What is a Module?
• 12.2  The math Module
• 12.3  The random Module
• 12.4  The statistics Module
• 12.5  The datetime Module
• 12.6  The os Module
• 12.7  The sys Module
• 12.8  Practical Exercises
• 12.9  Module Quiz (MCQs)
• 12.10  Module Assignment
• 12.11  Interview Questions — Module 12
• 12.12  Student Notes Page

Module 12: Python Modules

12.1  What is a Module?

A module is simply a file containing pre-written Python code (functions, classes, variables) that you can import and reuse in your own programs — saving you from reinventing the wheel for common tasks.

import math
from datetime import datetime
import random as rnd     # import with an alias

12.2  The math Module

Covered in detail in Module 4 — provides advanced mathematical functions.

import math
print(math.sqrt(81))     # 9.0
print(math.pi)           # 3.14159...

12.3  The random Module

The random module generates random numbers and selections — useful for simulations, sampling data, and generating test/dummy data.

import random

print(random.randint(1, 100))         # random whole number 1-100
print(random.choice(["A","B","C"]))   # random pick from a list

students = ["Priya", "Rahul", "Anita", "Vikram"]
random.shuffle(students)              # shuffles the list in place
print(students)

12.4  The statistics Module

The statistics module provides ready-made functions for common statistical calculations — a preview of what NumPy and Pandas will do at scale later in this course.

import statistics

marks = [78, 85, 92, 66, 88, 74]
print("Mean:", statistics.mean(marks))
print("Median:", statistics.median(marks))
print("Mode:", statistics.mode(marks))
print("Std Dev:", round(statistics.stdev(marks), 2))

12.5  The datetime Module

The datetime module handles dates and times — essential for timestamps, deadlines, reports, and scheduling logic.

from datetime import datetime, timedelta

now = datetime.now()
print("Current date & time:", now)
print("Formatted:", now.strftime("%d-%m-%Y"))

deadline = now + timedelta(days=7)
print("Assignment due:", deadline.strftime("%d-%m-%Y"))

12.6  The os Module

The os module lets Python interact with the operating system — checking folders, listing files, and managing paths.

import os

print(os.getcwd())              # current working directory
print(os.listdir("."))          # list files in current folder
os.makedirs("reports", exist_ok=True)   # create a folder safely

12.7  The sys Module

The sys module provides access to system-specific parameters, such as command-line arguments and the Python version being used.

import sys

print(sys.version)      # Python version info
# sys.exit()            # stops program execution immediately

12.8  Practical Exercises

Basic (5 Questions)

1. Generate a random number between 1 and 50 using the random module.

2. Print today's date using the datetime module.

3. Calculate the mean and median of a list of 6 numbers using statistics.

4. List all files in your current folder using the os module.

5. Print your installed Python version using the sys module.

Intermediate (5 Questions)

1. Shuffle a list of 10 student names using random.shuffle().

2. Calculate an assignment deadline 5 days from today using timedelta.

3. Find the standard deviation of a list of exam scores using statistics.stdev().

4. Create a new folder using os.makedirs() only if it doesn't already exist.

5. Format the current date as 'DD-Month-YYYY' (e.g. 15-March-2026) using strftime().

Advanced (5 Questions)

1. Build a random 'Quiz Question Picker' that selects 5 unique questions from a list of 20 using random.sample().

2. Build a program that calculates how many days remain until a given course start date.

3. Write a program that generates a summary report (mean, median, mode, std dev) for a marks dataset using statistics.

4. Build a simple file-organizer script using os that lists all files in a folder and counts how many are .csv vs .txt.

5. Combine datetime and random to build a 'Random Class Scheduler' that assigns random time slots to 5 courses this week.

12.9  Module Quiz (MCQs)

12.10  Module Assignment

Assignment: Random Quiz & Report Generator

• Create a list of 10 quiz questions (just strings).
• Use random.sample() to randomly select 5 questions for today's quiz.
• Generate a list of 20 dummy marks and calculate mean, median, and standard deviation.
• Print a report header showing today's date (formatted as DD-MM-YYYY) using datetime.

Expected Output: A working script combining random, statistics, and datetime modules to produce a mini quiz-and-results report.

12.11  Interview Questions — Module 12

• Q: What is the purpose of the import statement?
  A: import brings in pre-built code (functions, classes) from another module or library so you can reuse it without rewriting it.
• Q: What is the difference between random.random() and random.randint()?
  A: random.random() returns a random float between 0 and 1, while random.randint(a, b) returns a random integer between a and b, inclusive.
• Q: Why would you use the statistics module instead of manual calculations?
  A: It provides tested, ready-made functions (mean, median, mode, stdev) that are faster to use and less error-prone than writing the formulas manually.
• Q: What is the difference between the os and sys modules?
  A: os handles operating-system-level tasks like files and folders, while sys deals with the Python interpreter itself, such as command-line arguments and program exit.

12.12  Student Notes Page

Use this space to write down key points, doubts, and your own examples from today's session.