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from datetime import datetime
from typing import Callable, Optional, TypeVar
from reactivex import Observable, abc, typing
from reactivex.scheduler import TimeoutScheduler
_T = TypeVar("_T")
def throttle_first_(
window_duration: typing.RelativeTime, scheduler: Optional[abc.SchedulerBase] = None
) -> Callable[[Observable[_T]], Observable[_T]]:
def throttle_first(source: Observable[_T]) -> Observable[_T]:
"""Returns an observable that emits only the first item emitted
by the source Observable during sequential time windows of a
specified duration.
Args:
source: Source observable to throttle.
Returns:
An Observable that performs the throttle operation.
"""
def subscribe(
observer: abc.ObserverBase[_T],
scheduler_: Optional[abc.SchedulerBase] = None,
) -> abc.DisposableBase:
_scheduler = scheduler or scheduler_ or TimeoutScheduler.singleton()
duration = _scheduler.to_timedelta(window_duration or 0.0)
if duration <= _scheduler.to_timedelta(0):
raise ValueError("window_duration cannot be less or equal zero.")
last_on_next: Optional[datetime] = None
def on_next(x: _T) -> None:
nonlocal last_on_next
emit = False
now = _scheduler.now
with source.lock:
if not last_on_next or now - last_on_next >= duration:
last_on_next = now
emit = True
if emit:
observer.on_next(x)
return source.subscribe(
on_next, observer.on_error, observer.on_completed, scheduler=_scheduler
)
return Observable(subscribe)
return throttle_first
__all__ = ["throttle_first_"]
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