firestar5683
81 lines
2.8 KiB
Python
81 lines
2.8 KiB
Python
from typing import Callable, Optional, TypeVar, cast
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from reactivex import Observable, abc
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from reactivex.internal.basic import default_comparer, identity
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from reactivex.typing import Comparer, Mapper
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_T = TypeVar("_T")
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_TKey = TypeVar("_TKey")
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def distinct_until_changed_(
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key_mapper: Optional[Mapper[_T, _TKey]] = None,
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comparer: Optional[Comparer[_TKey]] = None,
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) -> Callable[[Observable[_T]], Observable[_T]]:
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key_mapper_ = key_mapper or cast(Callable[[_T], _TKey], identity)
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comparer_ = comparer or default_comparer
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def distinct_until_changed(source: Observable[_T]) -> Observable[_T]:
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"""Returns an observable sequence that contains only distinct
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contiguous elements according to the key_mapper and the
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comparer.
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Examples:
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>>> op = distinct_until_changed();
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>>> op = distinct_until_changed(lambda x: x.id)
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>>> op = distinct_until_changed(lambda x: x.id, lambda x, y: x == y)
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Args:
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key_mapper: [Optional] A function to compute the comparison
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key for each element. If not provided, it projects the
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value.
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comparer: [Optional] Equality comparer for computed key
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values. If not provided, defaults to an equality
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comparer function.
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Returns:
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An observable sequence only containing the distinct
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contiguous elements, based on a computed key value, from
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the source sequence.
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"""
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def subscribe(
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observer: abc.ObserverBase[_T],
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scheduler: Optional[abc.SchedulerBase] = None,
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) -> abc.DisposableBase:
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has_current_key = False
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current_key: _TKey = cast(_TKey, None)
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def on_next(value: _T) -> None:
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nonlocal has_current_key, current_key
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comparer_equals = False
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try:
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key = key_mapper_(value)
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except Exception as exception: # pylint: disable=broad-except
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observer.on_error(exception)
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return
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if has_current_key:
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try:
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comparer_equals = comparer_(current_key, key)
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except Exception as exception: # pylint: disable=broad-except
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observer.on_error(exception)
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return
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if not has_current_key or not comparer_equals:
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has_current_key = True
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current_key = key
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observer.on_next(value)
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return source.subscribe(
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on_next, observer.on_error, observer.on_completed, scheduler=scheduler
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)
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return Observable(subscribe)
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return distinct_until_changed
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__all__ = ["distinct_until_changed_"]
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