Learn: Collections

Four notebooks, in order. Each is self-contained, but together they cover the whole module — one container per notebook (with the smaller OrderedDict and ChainMap folded into the last).

Notebooks in this section

1. Counter — counting hashable things. Building a Counter from any iterable, most_common, the arithmetic operators (+, -, &, |), update/subtract, total, and elements.
2. defaultdict — a dict that supplies a default for missing keys. The grouping pattern (list), the counting pattern (int), sets and nesting, and how it compares to dict.setdefault.
3. deque — a double-ended queue with fast appends and pops at both ends. Why list.pop(0) is slow, appendleft/popleft, bounded deques with maxlen for sliding windows and history, and rotate.
4. namedtuple and friends — tuples with named fields: defining them, _replace, _asdict, _fields, and how they sit between a tuple and a class. Then OrderedDict (what it still offers now that dict keeps order) and ChainMap (layered lookups for configs and defaults).

After these, the Recipes cover task-focused applications and the Reference has quick lookups for every type.