Week-5-1

Introduction to Loops

• Loops: Control flow statements that execute code multiple times.

• While Loops: Executes code as long as a condition is true.

While Loop Structure

• Syntax: while condition: body

• Consists of while keyword, a boolean expression, and loop body.

• If true, body executes; if false, control passes to the next statement.

Loop Iterations

• Iteration: One execution cycle through the loop.

• Re-evaluates condition until false to exit the loop.

Example of a While Loop

• Initialization: current_power to 2, user_character to 'y'.

• Uses while user_character == 'y': to print current_power, double it, and read new input.

• Example flow: 2, 4, 8, exits on 'n'.

Incorporating Input with Sentinel Values

• Sentinel Values: Indicate end of data, e.g., 'Q'.

• Structure: while user_value != 'Q': continues until 'Q'.

Extracting Digits from Numbers

• Extract digits via while loop: while number > 0: prints last digit, reduces number.

• Example for 902: prints 2, 0, 9.

Handling Infinite Loops

• Occurs when condition is always true, freezing the program.

Example Program: Greatest Common Divisor (GCD)

• Algorithm with two integers A and B: while A != B: subtracts the smaller from the larger until equal.

• Example: A = 20, B = 15 results in GCD = 5.

Example Program: Conversation Simulation

• Uses while user_input != 'goodbye': for random responses based on input.

Example Program: Computing the Average

• Ends input with zero; sums and counts input until sentinel.

• Average calculated as {sum} / {count}.