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from typing import Any, Callable, Optional, TypeVar, cast
from reactivex import Observable, abc
from reactivex.disposable import MultipleAssignmentDisposable
from reactivex.scheduler import TimeoutScheduler
from reactivex.typing import Mapper, Predicate, RelativeTime
_TState = TypeVar("_TState")
def generate_with_relative_time_(
initial_state: _TState,
condition: Predicate[_TState],
iterate: Mapper[_TState, _TState],
time_mapper: Callable[[_TState], RelativeTime],
) -> Observable[_TState]:
"""Generates an observable sequence by iterating a state from an
initial state until the condition fails.
Example:
res = source.generate_with_relative_time(
0, lambda x: True, lambda x: x + 1, lambda x: 0.5
)
Args:
initial_state: Initial state.
condition: Condition to terminate generation (upon returning
false).
iterate: Iteration step function.
time_mapper: Time mapper function to control the speed of
values being produced each iteration, returning relative
times, i.e. either floats denoting seconds or instances of
timedelta.
Returns:
The generated sequence.
"""
def subscribe(
observer: abc.ObserverBase[_TState],
scheduler: Optional[abc.SchedulerBase] = None,
) -> abc.DisposableBase:
scheduler = scheduler or TimeoutScheduler.singleton()
mad = MultipleAssignmentDisposable()
state = initial_state
has_result = False
result: _TState = cast(_TState, None)
first = True
time: Optional[RelativeTime] = None
def action(scheduler: abc.SchedulerBase, _: Any) -> None:
nonlocal state
nonlocal has_result
nonlocal result
nonlocal first
nonlocal time
if has_result:
observer.on_next(result)
try:
if first:
first = False
else:
state = iterate(state)
has_result = condition(state)
if has_result:
result = state
time = time_mapper(state)
except Exception as e: # pylint: disable=broad-except
observer.on_error(e)
return
if has_result:
assert time
mad.disposable = scheduler.schedule_relative(time, action)
else:
observer.on_completed()
mad.disposable = scheduler.schedule_relative(0, action)
return mad
return Observable(subscribe)
__all__ = ["generate_with_relative_time_"]
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