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itertools
Iterator building blocks — `chain`, `groupby`, `combinations`, `accumulate`. Lazy, memory-friendly.
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Open lesson lesson-130 →Related — Standard library
pathlib.PathObject-oriented filesystem paths. `Path(".").rglob("*.py")` beats `os.walk + os.…collections.CounterDict subclass that counts hashable items: `Counter("hello")` → `{'l': 2, ...}`.functools.cacheMemoize a pure function with `@functools.cache`. Replaces hand-rolled dict cachi…dataclasses.fieldConfigure a dataclass attribute — mutable defaults, init/repr behavior. Use `fie…