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from typing import Callable, Optional, TypeVar
from reactivex import Observable, abc
_T = TypeVar("_T")
def default_if_empty_(
default_value: Optional[_T] = None,
) -> Callable[[Observable[_T]], Observable[Optional[_T]]]:
def default_if_empty(source: Observable[_T]) -> Observable[Optional[_T]]:
"""Returns the elements of the specified sequence or the
specified value in a singleton sequence if the sequence is
empty.
Examples:
>>> obs = default_if_empty(source)
Args:
source: Source observable.
Returns:
An observable sequence that contains the specified default
value if the source is empty otherwise, the elements of the
source.
"""
def subscribe(
observer: abc.ObserverBase[Optional[_T]],
scheduler: Optional[abc.SchedulerBase] = None,
) -> abc.DisposableBase:
found = [False]
def on_next(x: _T):
found[0] = True
observer.on_next(x)
def on_completed():
if not found[0]:
observer.on_next(default_value)
observer.on_completed()
return source.subscribe(
on_next, observer.on_error, on_completed, scheduler=scheduler
)
return Observable(subscribe)
return default_if_empty
__all__ = ["default_if_empty_"]
|
