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https://github.com/firestar5683/StarPilot.git
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firestar5683
84 lines
2.8 KiB
Python
84 lines
2.8 KiB
Python
from typing import Callable, Optional, TypeVar, cast
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from reactivex import Observable, abc, compose
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from reactivex import operators as ops
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from reactivex.internal.exceptions import SequenceContainsNoElementsError
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from reactivex.typing import Predicate
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_T = TypeVar("_T")
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def single_or_default_async_(
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has_default: bool = False, default_value: Optional[_T] = None
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) -> Callable[[Observable[_T]], Observable[_T]]:
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def single_or_default_async(source: Observable[_T]) -> Observable[_T]:
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def subscribe(
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observer: abc.ObserverBase[_T],
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scheduler: Optional[abc.SchedulerBase] = None,
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):
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value = cast(_T, default_value)
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seen_value = False
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def on_next(x: _T):
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nonlocal value, seen_value
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if seen_value:
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observer.on_error(
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Exception("Sequence contains more than one element")
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)
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else:
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value = x
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seen_value = True
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def on_completed():
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if not seen_value and not has_default:
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observer.on_error(SequenceContainsNoElementsError())
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else:
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observer.on_next(value)
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observer.on_completed()
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return source.subscribe(
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on_next, observer.on_error, on_completed, scheduler=scheduler
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)
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return Observable(subscribe)
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return single_or_default_async
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def single_or_default_(
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predicate: Optional[Predicate[_T]] = None, default_value: _T = None
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) -> Callable[[Observable[_T]], Observable[_T]]:
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"""Returns the only element of an observable sequence that matches
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the predicate, or a default value if no such element exists this
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method reports an exception if there is more than one element in the
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observable sequence.
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Examples:
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>>> res = single_or_default()
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>>> res = single_or_default(lambda x: x == 42)
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>>> res = single_or_default(lambda x: x == 42, 0)
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>>> res = single_or_default(None, 0)
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Args:
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predicate -- [Optional] A predicate function to evaluate for
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elements in the source sequence.
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default_value -- [Optional] The default value if the index is
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outside the bounds of the source sequence.
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Returns:
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An observable Sequence containing the single element in the
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observable sequence that satisfies the condition in the predicate,
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or a default value if no such element exists.
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"""
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if predicate:
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return compose(
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ops.filter(predicate), ops.single_or_default(None, default_value)
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)
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else:
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return single_or_default_async_(True, default_value)
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__all__ = ["single_or_default_", "single_or_default_async_"]
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