50 lines
1.2 KiB
Python
50 lines
1.2 KiB
Python
from __future__ import annotations
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import itertools
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from collections.abc import Callable, Iterable, Iterator
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from typing import Generic, Protocol, Self, TypeVar
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class SupportsLessThan(Protocol):
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def __lt__(self, other: Self, /) -> bool:
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raise NotImplementedError()
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T = TypeVar("T")
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KeyT = TypeVar("KeyT", bound=SupportsLessThan)
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GroupT = TypeVar("GroupT")
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def groupby(
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it: Iterable[T],
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key_fn: Callable[[T], KeyT],
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group_fn: Callable[[Iterable[T]], GroupT] = lambda x: x,
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) -> Iterator[tuple[KeyT, GroupT]]:
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for k, g in itertools.groupby(sorted(it, key=key_fn), key=key_fn):
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yield k, group_fn(g)
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U = TypeVar("U")
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V = TypeVar("V")
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def map_none(fn: Callable[[U], V], value: U | None) -> V | None:
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if value is None:
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return None
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return fn(value)
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class FnChain(Generic[U]):
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def __init__(self, fn: Callable[[], U], /):
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self._fn: Callable[[], U] = fn
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def __or__(self, next_fn: Callable[[U], V], /) -> FnChain[V]:
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return FnChain(lambda: next_fn(self._fn()))
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def result(self) -> U:
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return self._fn()
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@classmethod
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def transform(cls, x: V, /) -> FnChain[V]:
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return FnChain(lambda: x)
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