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import asyncio
from asyncio import Future
from typing import Any, Optional, TypeVar, cast
from reactivex import Observable, abc
from reactivex.disposable import Disposable
_T = TypeVar("_T")
def from_future_(future: "Future[_T]") -> Observable[_T]:
"""Converts a Future to an Observable sequence
Args:
future -- A Python 3 compatible future.
https://docs.python.org/3/library/asyncio-task.html#future
Returns:
An Observable sequence which wraps the existing future success
and failure.
"""
def subscribe(
observer: abc.ObserverBase[Any], scheduler: Optional[abc.SchedulerBase] = None
) -> abc.DisposableBase:
def done(future: "Future[_T]") -> None:
try:
value: Any = future.result()
except Exception as ex:
observer.on_error(ex)
except asyncio.CancelledError as ex: # pylint: disable=broad-except
# asyncio.CancelledError is a BaseException, so need to cast
observer.on_error(cast(Exception, ex))
else:
observer.on_next(value)
observer.on_completed()
future.add_done_callback(done)
def dispose() -> None:
if future:
future.cancel()
return Disposable(dispose)
return Observable(subscribe)
__all__ = ["from_future_"]
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