Iterating over collections
A for loop asks an iterable for its values one at a time. Lists, tuples, strings, dictionaries, files, ranges and generators can all be iterated.
Use Python's iteration tools
Use enumerate() when you need an index and value, items() for dictionary key-value pairs and range() when a numeric sequence is actually required. Avoid manually managing an index when direct iteration is clearer.
Keep the loop body focused
If a loop contains validation, database calls, formatting and multiple nested decisions, move part of the work into named functions. This makes the algorithm easier to test and understand.
Practice: iterate over a list of products, calculate totals and print only products whose price exceeds a chosen threshold.
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