Advanced Loops

What You Might Be Wondering

"I can write loops already. Why is there an advanced lesson?"

Because most loop bugs aren't about "can you loop" — they're about exit timing and fallback logic.

One-Line Definition

Advanced loops are about fine-grained flow control: for...else, nested loops, and search patterns.

Real-Life Analogy

Looking for a book:

• Found it? Stop searching.
• Searched everywhere and didn't find it? Then show "not found."

That's for...else.

Minimal Working Example (for...else)

nums = [1, 3, 5, 7]
target = 4

for n in nums:
    if n == target:
        print("Found")
        break
else:
    print("Not found")

Nested Loops

for row in range(1, 4):
    for col in range(1, 4):
        print(f"({row},{col})", end=" ")
    print()

Search Pattern (Worth Memorizing)

found = False
for item in items:
    if condition_met:
        found = True
        break

if not found:
    print("No match")

Quick Quiz (5 min)

1. Use for...else to search for a username.
2. Print a 9x9 multiplication table.
3. Search a 2D list for a target value and output its coordinates.

Quiz Rubric & Grading Criteria

• Direction: write runnable code that covers the core requirements and edge cases from the prompt.
• Criterion 1 (Correctness): main flow produces correct results, key branches execute.
• Criterion 2 (Readability): clear variable names, no excessive nesting.
• Criterion 3 (Robustness): basic protection against empty values, type errors, or unexpected input.

Take-Home Task

Build an "inventory lookup":

• Input: a 2D product table
• Find the target SKU, output its position, and stop
• If not found, output a message

Acceptance Criteria

You can independently:

• Explain when for...else's else block actually runs
• Write maintainable nested loops
• Use the search-match-exit pattern

Common Errors & Debugging Steps (Beginner Edition)

• Error message looks like gibberish: read the last line for the error type (TypeError, NameError, etc.), then trace back to the offending line.
• Not sure what a variable holds: drop a temporary print(variable, type(variable)) to check.
• Changed code but nothing happened: make sure you saved the file, you're running the right file, and your terminal environment (venv) is correct.

Common Misconceptions

• Misconception: for...else's else runs every time.

• Reality: it only runs if the loop completes without hitting a break.

• Misconception: deeply nested loops are fine if they work.

• Reality: past two levels, extract the inner logic into a function.