97 lines
2.2 KiB
Python
97 lines
2.2 KiB
Python
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"""
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A coroutine to compute a running average.
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Testing ``averager2`` by itself::
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# tag::RETURNING_AVERAGER_DEMO_1[]
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>>> coro_avg = averager2()
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>>> next(coro_avg)
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>>> coro_avg.send(10) # <1>
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>>> coro_avg.send(30)
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>>> coro_avg.send(6.5)
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>>> coro_avg.close() # <2>
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# end::RETURNING_AVERAGER_DEMO_1[]
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Catching `StopIteration` to extract the value returned by
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the coroutine::
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# tag::RETURNING_AVERAGER_DEMO_2[]
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>>> coro_avg = averager2()
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>>> next(coro_avg)
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>>> coro_avg.send(10)
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>>> coro_avg.send(30)
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>>> coro_avg.send(6.5)
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>>> try:
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... coro_avg.send(STOP) # <1>
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... except StopIteration as exc:
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... result = exc.value # <2>
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...
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>>> result # <3>
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Result(count=3, average=15.5)
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# end::RETURNING_AVERAGER_DEMO_2[]
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Using `yield from`:
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# tag::RETURNING_AVERAGER_DEMO_3[]
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>>> def compute():
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... res = yield from averager2(True) # <1>
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... print('computed:', res) # <2>
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... return res # <3>
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...
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>>> comp = compute() # <4>
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>>> for v in [None, 10, 20, 30, STOP]: # <5>
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... try:
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... comp.send(v) # <6>
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... except StopIteration as exc: # <7>
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... result = exc.value
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received: 10
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received: 20
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received: 30
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received: <Sentinel>
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computed: Result(count=3, average=20.0)
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>>> result # <8>
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Result(count=3, average=20.0)
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# end::RETURNING_AVERAGER_DEMO_3[]
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"""
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# tag::RETURNING_AVERAGER_TOP[]
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from collections.abc import Generator
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from typing import Union, NamedTuple
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class Result(NamedTuple): # <1>
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count: int # type: ignore # <2>
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average: float
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class Sentinel: # <3>
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def __repr__(self):
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return f'<Sentinel>'
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STOP = Sentinel() # <4>
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SendType = Union[float, Sentinel] # <5>
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# end::RETURNING_AVERAGER_TOP[]
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# tag::RETURNING_AVERAGER[]
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def averager2(verbose: bool = False) -> Generator[None, SendType, Result]: # <1>
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total = 0.0
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count = 0
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average = 0.0
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while True:
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term = yield # <2>
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if verbose:
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print('received:', term)
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if isinstance(term, Sentinel): # <3>
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break
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total += term # <4>
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count += 1
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average = total / count
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return Result(count, average) # <5>
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# end::RETURNING_AVERAGER[]
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