Built-in collection types

Python’s collection types include sequence (string, tuple, list) and mapping types (dictonaries).

They also include sets.

Collection types in collections

Deque

A Python deque can be of fixed size or unbounded. You can append to either end and pop from either end. Appending or popping has O(1) complexity, versus O(N) for a list.

Using a fixed-size deque to track recent history:

>>> from collections import deque
>>> hist = deque(maxlen=3)
>>> for x in [1, 2, 3, 4, 5]:
    hist.append(x)
>>> hist
deque([3, 4, 5], maxlen=3)