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