Core Python

Chapter 3 — Python Flow Control

📚 Chapter Overview

A script that just runs top-to-bottom is limited. In this chapter, you will learn how to make your Python scripts intelligent using if-elif-else logic and how to handle repetitive tasks using for and while loops.

Learning Objectives:

3.1 The If-Elif-Else Ladder

Part 1 — Definition

Conditional statements in Python rely on Indentation instead of curly braces. The elif (short for else-if) allows you to check multiple conditions in a sequence. If the first condition is false, it moves to the next elif, and finally to else if nothing matches.

Part 2 — Syntax

if condition:
    # Code
elif another_condition:
    # Code
else:
    # Code

Part 3 — Example

Problem: Categorize a student based on their score.

script.py 
score = 85
if score >= 90:
    print("Grade A")
elif score >= 75:
    print("Grade B")
else:
    print("Grade C")

Output: Grade B

Part 4 — Video

Video: Coming Soon

3.2 Loops (For & While)

Part 1 — Definition

Loops repeat a block of code. Python's for loop is mostly used to iterate over a sequence (like a list or a range of numbers). The while loop continues as long as a condition is met.

Part 2 — Syntax

for i in range(5):
    # Runs 5 times
while condition:
    # Runs till false

Part 3 — Example

Problem: Sum all numbers from 1 to user-input.

script.py 
limit = int(input("Enter limit: "))
total = 0
for i in range(1, limit + 1):
    total += i
print(f"Total Sum: {total}")

Part 4 — Video

Video: Coming Soon

🏆 Chapter Challenge

Challenge Objective

Create a "Password Strength Checker" that uses logic and loop controls.

Requirements

Step-by-Step Process

  1. Use len(password) to check length.
  2. Use a for loop to inspect each character.
  3. Print a status: "Strong", "Weak", or "Invalid".

Expected Deliverables

Solve in Compiler