Python #1 Fundamentals

🐍 CS25C02 Python Study Hub

OverviewProblem SolvingAlgorithmPython ModesVariablesOperatorsBuilt-insPracticeQuiz

Unit I · Introduction to Python

Think logically.
Code creatively.

Interactive study material for CS25C02 – Computer Programming: Python. Learn the fundamentals through explanations, worked examples, short activities, and a live Python runner in every topic.

📘 Beginner-friendly notes▶ Run Python in browser🧩 Practice + quiz📱 Mobile-friendly

Study progress

0 of 6 topics completed

Unit I learning path

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1. Problem Solving

Identify inputs, processing steps, and expected outputs.

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2. Algorithms

Represent solutions with algorithms, flowcharts, and pseudocode.

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3. Python Modes

Understand interactive mode, scripts, comments, indentation, and errors.

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4. Variables & Types

Store values and work with Python's basic data types.

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5. Operators

Evaluate arithmetic expressions and operator precedence.

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6. Built-ins & Imports

Use built-in functions and import tools from modules.

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1. Problem solving and problem analysis

Problem solving means understanding a task and developing a clear sequence of steps to produce the required result. A problem analysis chart records the inputs, processing, and outputs before coding.

Worked example: Area of a rectangle

Input	Processing	Output
Length and breadth	Area = length × breadth	Area of rectangle

Method: identify the known values, choose the formula, calculate the result, and display it.

▶ Python Lab 1 · Rectangle areaEdit the code, then run it.

length = 12 breadth = 5 area = length * breadth print("Length:", length) print("Breadth:", breadth) print("Area of rectangle:", area)

Ready. Click Run Python to execute this code.

Output will appear here.

I can describe a problem using input, process, and output.

2. Algorithms, flowcharts, and pseudocode

An algorithm is a finite sequence of unambiguous steps that solves a problem. A flowchart uses symbols and arrows to show the steps visually. Pseudocode describes the logic in plain, structured language without strict programming syntax.

Flowchart symbol	Purpose
Oval	Start / End
Parallelogram	Input / Output
Rectangle	Processing / calculation
Diamond	Decision, such as Yes / No
Arrow	Direction of flow

Pseudocode: larger of two numbers

START
INPUT a, b
IF a > b THEN
    DISPLAY a
ELSE
    DISPLAY b
END IF
STOP

▶ Python Lab 2 · Larger of two numbersTry changing a and b.

a = 18 b = 25 if a > b: print("Larger number:", a) elif b > a: print("Larger number:", b) else: print("Both numbers are equal")

Ready. Click Run Python to execute this code.

Output will appear here.

I can write a simple algorithm and convert it to Python.

3. Interactive mode, script mode, comments, indentation, and errors

Interactive mode: type an expression at the Python prompt and see the result immediately. Script mode: save statements in a .py file and run the file.

• Comments: start with #; Python ignores them during execution.
• Indentation: spaces at the start of a line define a code block. Four spaces are the common convention.
• Syntax error: code breaks Python's grammar.
• Runtime error: an error occurs while the program is running.
• Logic error: the program runs but produces the wrong answer.

▶ Python Lab 3 · Comments and indentationTry changing the score.

# A simple script with a comment score = 82 if score >= 50: print("Result: Pass") print("Congratulations!") else: print("Result: Try again") print("Program finished.")

Ready. Click Run Python to execute this code.

Output will appear here.

I can identify comments and explain why indentation matters.

4. Variables, reserved words, and data types

A variable is a name that refers to a value. Python determines a value's type at runtime. Use descriptive names such as student_name and total_marks.

Identifier rules

• Start with a letter or underscore; do not start with a digit.
• Use letters, digits, and underscores only.
• Names are case-sensitive: score and Score differ.
• Do not use reserved keywords such as if, for, class, or return.

Type	Example	Meaning
int	age = 19	Integer
float	height = 1.72	Decimal number
str	name = "Jamal"	Text
bool	passed = True	True or False
NoneType	value = None	No value assigned

▶ Python Lab 4 · Variables and typesChange values or add another variable.

student_name = "Jamal" age = 19 average = 87.5 is_enrolled = True print(student_name, "has these values:") print("age =", age, "| type =", type(age).__name__) print("average =", average, "| type =", type(average).__name__) print("is_enrolled =", is_enrolled, "| type =", type(is_enrolled).__name__)

Ready. Click Run Python to execute this code.

Output will appear here.

I can create variables and identify common Python data types.

5. Arithmetic operators and expressions

Operator	Operation	Example	Result
+	Addition	7 + 2	9
-	Subtraction	7 - 2	5
*	Multiplication	7 * 2	14
/	True division	7 / 2	3.5
//	Floor division	7 // 2	3
%	Remainder	7 % 2	1
**	Exponentiation	7 ** 2	49

Parentheses can make the intended order clear. In general, exponentiation is evaluated before multiplication and division, which are evaluated before addition and subtraction.

▶ Python Lab 5 · Expressions and precedenceExperiment with the expressions.

a = 17 b = 5 print("a + b =", a + b) print("a - b =", a - b) print("a * b =", a * b) print("a / b =", a / b) print("a // b =", a // b) print("a % b =", a % b) print("a ** 2 =", a ** 2) print("2 + 3 * 4 =", 2 + 3 * 4) print("(2 + 3) * 4 =", (2 + 3) * 4)

Ready. Click Run Python to execute this code.

Output will appear here.

I can choose the correct arithmetic operator and predict expression results.

6. Built-in functions and importing from packages

Python provides built-in functions that are ready to use. A module is a file containing Python definitions and statements. Import a module to use additional functionality.

Function	Example	Purpose
print()	print("Hello")	Display output
type()	type(4.2)	Inspect a value's type
len()	len("Python")	Count items
sum()	sum([2, 3, 4])	Add values
max() / min()	max([2, 9, 4])	Find largest / smallest

Example import: import math makes names such as math.sqrt() and math.pi available.

▶ Python Lab 6 · Built-ins and math moduleTry a different radius.

import math numbers = [4, 9, 16, 25] radius = 3 print("Numbers:", numbers) print("Count:", len(numbers)) print("Sum:", sum(numbers)) print("Largest:", max(numbers)) print("Square root of 81:", math.sqrt(81)) print("Circle radius:", radius) print("Circle area:", round(math.pi * radius ** 2, 2))

Ready. Click Run Python to execute this code.

Output will appear here.

I can use built-in functions and import a module.

Practical activities

Complete these exercises by editing the relevant code lab. Check each task after you have run and understood your solution.

Write a program to calculate the perimeter of a rectangle.

Write an algorithm and pseudocode to convert Celsius to Fahrenheit.

Display a person's name, age, and data types.

Calculate the quotient and remainder for two integers.

Use a function from the math module to calculate a circle's area.

🧩 Quick self-check quiz

Choose one answer for each question, then check your score.

1. Which stage calculates the result in an IPO chart? Input Process Output

2. Which flowchart symbol represents a decision? Oval Rectangle Diamond

3. Which character begins a Python comment? # // <!--

4. What is the type of 3.5? int float str

5. What is 17 % 5? 3 2 0

6. Which statement imports the math module? get math include math import math

Recommended references

• Allen B. Downey, Think Python: How to Think Like a Computer Scientist, 2nd edition, 2016.
• Karl Beecher, Computational Thinking: A Beginner's Guide to Problem Solving and Programming, 2017.
• Official Python Tutorial
• Pyodide Quickstart Documentation

🐍 CS25C02 Python Study Hub · Learn, run, test, debug, and create.