Concepts: Collections

Short essays on the ideas behind the collections module. Read these once and keep coming back to them when you're deciding how to store something.

Essays in this section

• Why specialised containers — what Counter, deque, and the rest buy you over a plain dict or list: not just speed (though list.pop(0) really is slow), but code that says what it means.
• Choosing a container — a decision guide across the whole module and the built-ins: Counter versus a manual count, defaultdict versus setdefault, deque versus list, namedtuple versus dict versus dataclass.