Loops and Iteration

Learning Objectives: After this lesson, you'll master for and while loops to repeat operations efficiently, understand iteration patterns, and learn loop control with break and continue.

Why Do We Need Loops?

Imagine you need to print "Hello" 100 times. Without loops, you'd write:

python
print("Hello")
print("Hello")
print("Hello")
# ... 97 more times!
Copy

Loops let you repeat code efficiently. They're essential for:

• Processing collections of data
• Repeating operations
• Automating repetitive tasks
• Building interactive programs

For Loops: Iterating Over Collections

The for loop is perfect when you know what you want to iterate over:

The range() Function

range() is your best friend for creating number sequences:

While Loops: Repeating Until a Condition is Met

While loops continue as long as a condition is True:

Loop Control: break and continue

Control loop execution with break and continue:

Nested Loops

Loops inside loops for multi-dimensional processing:

Loop Visualization

Let's visualize how loops work:

Common Loop Patterns

Pattern 1: Accumulation

Pattern 2: Building New Collections

Pattern 3: Finding Items

Practical Examples

Example 1: Grade Calculator

Example 2: Number Guessing Game

Practice Exercises

Exercise 1: Sum Calculator

Exercise 2: Pattern Generator

Exercise 3: List Processing

Key Takeaways

✅ For loops iterate over collections (lists, strings, ranges)
✅ While loops repeat while a condition is true
✅ range() generates number sequences: range(start, stop, step)
✅ break exits a loop early
✅ continue skips to the next iteration
✅ Nested loops handle multi-dimensional data
✅ Common patterns - accumulation, filtering, searching, building collections

Next Steps

In the next lesson, we'll dive deep into functions - how to create reusable code blocks, understand parameters and return values, and explore scope concepts.

Ready to make your code more organized and reusable? The next lesson will teach you the power of functions!