firestar5683
76 lines
2.3 KiB
Python
76 lines
2.3 KiB
Python
from sys import maxsize
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from typing import Any, Callable, List, Optional, TypeVar
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from reactivex import Observable
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from reactivex import operators as ops
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_T = TypeVar("_T")
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# pylint: disable=redefined-builtin
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def slice_(
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start: Optional[int] = None, stop: Optional[int] = None, step: Optional[int] = None
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) -> Callable[[Observable[_T]], Observable[_T]]:
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_start: int = 0 if start is None else start
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_stop: int = maxsize if stop is None else stop
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_step: int = 1 if step is None else step
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pipeline: List[Callable[[Observable[Any]], Observable[Any]]] = []
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def slice(source: Observable[_T]) -> Observable[_T]:
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"""The partially applied slice operator.
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Slices the given observable. It is basically a wrapper around the operators
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:func:`skip <reactivex.operators.skip>`,
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:func:`skip_last <reactivex.operators.skip_last>`,
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:func:`take <reactivex.operators.take>`,
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:func:`take_last <reactivex.operators.take_last>` and
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:func:`filter <reactivex.operators.filter>`.
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The following diagram helps you remember how slices works with streams.
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Positive numbers are relative to the start of the events, while negative
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numbers are relative to the end (close) of the stream.
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.. code::
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r---e---a---c---t---i---v---e---!
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0 1 2 3 4 5 6 7 8
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-8 -7 -6 -5 -4 -3 -2 -1 0
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Examples:
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>>> result = source.slice(1, 10)
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>>> result = source.slice(1, -2)
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>>> result = source.slice(1, -1, 2)
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Args:
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source: Observable to slice
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Returns:
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A sliced observable sequence.
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"""
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if _stop >= 0:
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pipeline.append(ops.take(_stop))
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if _start > 0:
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pipeline.append(ops.skip(_start))
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elif _start < 0:
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pipeline.append(ops.take_last(-_start))
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if _stop < 0:
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pipeline.append(ops.skip_last(-_stop))
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if _step > 1:
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pipeline.append(ops.filter_indexed(lambda x, i: i % _step == 0))
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elif _step < 0:
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# Reversing events is not supported
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raise TypeError("Negative step not supported.")
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return source.pipe(*pipeline)
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return slice
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__all__ = ["slice_"]
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