Loops

On This Page

• 6.1  while Loop
• 6.2  for Loop
• 6.3  The range() Function
• 6.4  Nested Loops
• 6.5  break, continue, pass
• 6.6  Loop Flowchart & Logical Thinking
• 6.7  Pattern Programs
• 6.8  Practical & Logic Building Exercises
• 6.9  Module Quiz (MCQs)
• 6.10  Module Assignment
• 6.11  Interview Questions — Module 6
• 6.12  Student Notes Page

Module 6: Loops

6.1  while Loop

A while loop repeats a block of code as long as a given condition remains True. It is best used when you don't know in advance how many times you need to repeat.

count = 1
while count <= 5:
    print("Batch", count)
    count += 1   # IMPORTANT: update the counter

6.2  for Loop

A for loop iterates over a sequence (list, string, range, etc.) — it is the most commonly used loop in Python, especially for data analytics tasks.

courses = ["SEO", "Google Ads", "Meta Ads"]
for course in courses:
    print("Course:", course)

6.3  The range() Function

The range() function generates a sequence of numbers, most often used to control how many times a for loop repeats.

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

6.4  Nested Loops

A nested loop is a loop inside another loop — the inner loop completes all its iterations for every single iteration of the outer loop. Commonly used for grids, tables, and patterns.

for i in range(1, 4):          # outer loop
    for j in range(1, 4):      # inner loop
        print(f"({i},{j})", end=" ")
    print()   # new line after each outer iteration

6.5  break, continue, pass

for i in range(1, 11):
    if i == 6:
        break        # stop the loop completely at 6
    if i % 2 == 0:
        continue     # skip even numbers, go to next iteration
    print(i)

6.6  Loop Flowchart & Logical Thinking

Visualizing a loop as a flowchart helps beginners understand exactly when a loop repeats and when it stops.

Figure 6.1 — Loop execution flow: the condition is checked before every repetition; the loop exits the moment the condition becomes False.

6.7  Pattern Programs

Pattern programs are a classic way to build strong nested-loop logic. Here are two common examples:

rows = 5
for i in range(1, rows+1):
    print("*" * i)

rows = 4
for i in range(1, rows+1):
    for j in range(1, i+1):
        print(j, end=" ")
    print()

6.8  Practical & Logic Building Exercises

Basic (5 Questions)

1. Print numbers 1 to 10 using a for loop.

2. Print numbers 10 down to 1 using a while loop.

3. Print all even numbers between 1 and 20 using range() with a step.

4. Print the multiplication table of 7 using a for loop.

5. Use a while loop to print 'Learning Python' 5 times.

Intermediate (5 Questions)

1. Write a program to calculate the sum of all numbers from 1 to 100 using a loop.

2. Print a right-angled triangle pattern of stars for n rows (take n as input).

3. Use break to stop a loop as soon as it finds the first number divisible by 7 in a range.

4. Use continue to print only odd numbers between 1 and 30.

5. Write a nested loop to print a 5x5 grid of asterisks.

Advanced (5 Questions)

1. Write a program to check if a number is prime using a for loop and break.

2. Print a pyramid pattern of numbers as shown in this module, but reversed (largest row first).

3. Write a program to reverse a string using a while loop (without using slicing).

4. Build a simple 'Attendance Counter': loop through a list of student statuses and count Present vs Absent.

5. Write a program that prints the Fibonacci series up to n terms using a while loop.

6.9  Module Quiz (MCQs)

6.10  Module Assignment

Assignment: Student Attendance & Fee Tracker

• Create a list of 10 student names.
• Use a for loop to print each student's name with a serial number (1 to 10).
• Use continue to skip printing for any name that starts with the letter 'X'.
• Use break to stop the loop early if you reach a name called 'STOP' (add this as the 8th item to test it).

Expected Output: A numbered list of student names printed correctly, correctly skipping any 'X' names and stopping immediately upon reaching 'STOP'.

6.11  Interview Questions — Module 6

• Q: What is the difference between a for loop and a while loop?
  A: A for loop is used when the number of iterations is known or based on a sequence, while a while loop repeats based purely on a condition remaining True, useful when the count isn't known in advance.
• Q: What causes an infinite loop, and how do you avoid it?
  A: An infinite loop happens when the loop's condition never becomes False, usually because the counter or condition variable is never updated inside the loop body.
• Q: What is the difference between break and continue?
  A: break exits the loop entirely, while continue skips only the current iteration and moves on to the next one.
• Q: Why are nested loops useful in data analytics?
  A: Nested loops are used to process 2-dimensional data structures such as tables, matrices, or grids, where every row needs to be checked against every column.

6.12  Student Notes Page

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