Flow of Control in Python

1) Hook — The Traffic Signal and Your Python Code

Imagine you are crossing a busy street in Mumbai. The traffic signal controls when you walk, stop, or wait. Similarly, in Python programming, flow of control decides which part of the code runs and when. Just like you don’t cross on a red light, Python doesn’t execute every line sequentially—it follows conditions and loops to control the “traffic” of your program.

2) Core Concepts — Understanding Flow of Control in Python

Python provides three main ways to control the flow of your program:

• Conditional Statements — Make decisions using if, if-else, and if-elif-else.
• Loops — Repeat actions using for and while loops.
• Control Statements — Modify loop behavior with break, continue, and pass.

Conditional Statements

They allow your program to take decisions based on conditions.

if marks >= 33:
    print("Pass")

if age >= 18:
    print("Adult")
else:
    print("Minor")

if marks >= 90:
    print("A Grade")
elif marks >= 75:
    print("B Grade")
else:
    print("C Grade")

Loops

Loops help repeat a block of code multiple times.

for i in range(1,6):
    print(i)

count = 1
while count <= 5:
    print(count)
    count += 1

Control Statements in Loops

• break: Exits the loop immediately.
• continue: Skips the current iteration and continues with the next.
• pass: Does nothing; used as a placeholder.

Example:

for i in range(1, 6):
    if i == 3:
        break  # Loop stops when i is 3
    print(i)
  

3) Key Formulas/Rules

4) Did You Know?

Python was named after the British comedy group Monty Python — not the snake! Its creator, Guido van Rossum, wanted a name that was short, unique, and slightly mysterious. Just like Monty Python’s sketches, Python code is designed to be fun and readable.

5) Exam Tips — Common Mistakes & Board Exam Patterns

• Indentation Errors: Always indent blocks under if, for, while, and else. Missing or inconsistent indentation leads to errors.
• Colon (:): Don’t forget the colon at the end of control statements (e.g., if condition:).
• Logical Conditions: Use correct operators like == for comparison, not = (assignment).
• Loop Boundaries: Remember range(1,6) runs from 1 to 5, not 6.
• Practice Writing: Previous CBSE questions often ask for writing programs using if-else and loops, or to trace output of given code.

Previous Year Question Pattern Examples:

• Write a Python program to check if a student has passed or failed based on marks.
• Trace the output of a loop that prints numbers from 1 to 10 but skips multiples of 3.
• Write a program using if-elif-else to assign grades based on marks.