Concepts: Iterators and generators

Short essays on the ideas behind iteration in Python. Read these once and keep coming back to them when you're deciding how to shape data-processing code.

Essays in this section

• Laziness and memory — why lazy evaluation matters, when it's worth the complexity, and the trade-offs against eager approaches.
• Iteration as an interface — how the iterator protocol is really a contract that lets completely different types plug into the same tools (for, sum, list comprehensions, itertools), and why that makes Python's ecosystem compose so well.