firestar5683
41 lines
1.1 KiB
Python
41 lines
1.1 KiB
Python
from typing import Callable, Optional, TypeVar
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from reactivex import Observable, compose
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from reactivex import operators as ops
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from reactivex.typing import Predicate
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from ._firstordefault import first_or_default_async_
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_T = TypeVar("_T")
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def first_(
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predicate: Optional[Predicate[_T]] = None,
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) -> Callable[[Observable[_T]], Observable[_T]]:
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"""Returns the first element of an observable sequence that
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satisfies the condition in the predicate if present else the first
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item in the sequence.
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Examples:
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>>> res = res = first()(source)
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>>> res = res = first(lambda x: x > 3)(source)
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Args:
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predicate -- [Optional] A predicate function to evaluate for
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elements in the source sequence.
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Returns:
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A function that takes an observable source and returns an
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observable sequence containing the first element in the
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observable sequence that satisfies the condition in the predicate if
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provided, else the first item in the sequence.
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"""
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if predicate:
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return compose(ops.filter(predicate), ops.first())
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return first_or_default_async_(False)
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__all__ = ["first_"]
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