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Python Loops

Control Flow Focus

Python Loops

Looping is fundamental. Learn when to use for vs while, how to break/continue cleanly, and how to pair loops with helper functions.

Master for loopsUnderstand loop else

For loop basics​

for user in users:
    if not user.active:
        continue
    send_email(user)
  • enumerate gives indexes.
  • zip iterates multiple sequences in lockstep.

While loops​

while queue:
    job = queue.pop(0)
    handle(job)

Use while loops when the number of iterations isn't predetermined.

Loop else​

for item in items:
    if item.id == target:
        break
else:
    raise LookupError("Not found")

else executes if the loop completes without hitting break.

Nested loops​

Keep them shallow; extract logic into helper functions or comprehensions when possible.

Comprehensions vs loops​

  • Use comprehensions for building lists/dicts/sets in a single expression.
  • Stick with explicit loops when logic spans multiple statements or requires exception handling.

Next up in your learning path

Loop control keywords

Practice break, continue, and pass.

Companion

List comprehensions

Transform loops into concise expressions.

Reference

Generators

Yield values lazily for large datasets.

Next cluster

Frequently Asked Questions

Is there a do-while loop?

No built-in do-while. Emulate with `while True` and break once the condition fails.

How do I loop with indexes?

Use `enumerate(iterable, start=0)` to get index + value instead of managing counters manually.

When should I use recursion instead of loops?

Recursion shines for tree/graph problems or divide-and-conquer algorithms. For most everyday cases, loops are simpler and avoid recursion depth limits.