What do enumerate and zip do?

Question presented to candidate: "I often see loops like for i in range(len(items)). What do enumerate and zip do, how would you use them to clean that up, and is there anything surprising about how they behave?"

What a strong answer should cover:

• enumerate(iterable, start=0) yields (index, item) pairs, so you never index back into the list; start= sets the first number.
• zip(a, b, ...) yields tuples that take one item from each input, and stops as soon as the shortest input runs out.
• Both return lazy, single-use iterators (iter(e) is e), not lists; they work on any iterable, including generators and infinite ones.
• zip(..., strict=True) (Python 3.10, PEP 618) raises ValueError on a length mismatch; itertools.zip_longest pads instead.
• Idioms: dict(zip(keys, values)), zip(*rows) to transpose or unzip, enumerate(zip(a, b)) for index plus pairs.
• The lost-item gotcha: zip pulls from the left input first, so an iterator passed on the left loses one item when a later input runs out.

Code / implementation expected: Yes — rewrite an index loop with enumerate, walk two lists with zip, and show zip(*rows) or dict(zip(...)).