List Comprehensions

Why this matters

Comprehensions are the idiomatic Python filter/map — libraries like pandas, Django ORM chains, and FastAPI dependency wiring lean on them for readable one-pass transforms. Reviewers reject for loops that append to a list when a comprehension fits.

Common pitfalls

• Nesting three levels deep for cleverness — split into a helper or a real for loop once readability drops.
• Building a huge list just to iterate once — swap [...] for a generator (...) to avoid the memory spike.
• Late-binding closures inside lambda x: ... comprehensions — bind with lambda x, v=v: ... explicitly.