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from typing import Any, Callable, Optional, TypeVar
from reactivex import Observable, abc
from reactivex import operators as ops
from reactivex import typing
from reactivex.internal.exceptions import SequenceContainsNoElementsError
_T = TypeVar("_T")
def last_or_default_async(
source: Observable[_T],
has_default: bool = False,
default_value: Optional[_T] = None,
) -> Observable[Optional[_T]]:
def subscribe(
observer: abc.ObserverBase[Optional[_T]],
scheduler: Optional[abc.SchedulerBase] = None,
):
value = [default_value]
seen_value = [False]
def on_next(x: _T) -> None:
value[0] = x
seen_value[0] = True
def on_completed():
if not seen_value[0] and not has_default:
observer.on_error(SequenceContainsNoElementsError())
else:
observer.on_next(value[0])
observer.on_completed()
return source.subscribe(
on_next, observer.on_error, on_completed, scheduler=scheduler
)
return Observable(subscribe)
def last_or_default(
default_value: Optional[_T] = None, predicate: Optional[typing.Predicate[_T]] = None
) -> Callable[[Observable[_T]], Observable[Any]]:
def last_or_default(source: Observable[Any]) -> Observable[Any]:
"""Return last or default element.
Examples:
>>> res = _last_or_default(source)
Args:
source: Observable sequence to get the last item from.
Returns:
Observable sequence containing the last element in the
observable sequence.
"""
if predicate:
return source.pipe(
ops.filter(predicate),
ops.last_or_default(default_value),
)
return last_or_default_async(source, True, default_value)
return last_or_default
__all__ = ["last_or_default", "last_or_default_async"]
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