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raise ValueError('step must be non-zero')
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if start is None:
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start, stop = 0.0, stop * 1.0
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else:
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# swap when all args are used
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stop, start = start * 1.0, stop * 1.0
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cur = start
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while cur < stop:
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yield cur
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cur += step"
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4964,"def frange(stop, start=None, step=1.0):
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""""""A :func:`range` clone for float-based ranges.
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>>> frange(5)
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[0.0, 1.0, 2.0, 3.0, 4.0]
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>>> frange(6, step=1.25)
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[0.0, 1.25, 2.5, 3.75, 5.0]
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>>> frange(100.5, 101.5, 0.25)
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[100.5, 100.75, 101.0, 101.25]
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>>> frange(5, 0)
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[]
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>>> frange(5, 0, step=-1.25)
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[5.0, 3.75, 2.5, 1.25]
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""""""
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if not step:
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raise ValueError('step must be non-zero')
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if start is None:
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start, stop = 0.0, stop * 1.0
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else:
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# swap when all args are used
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stop, start = start * 1.0, stop * 1.0
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count = int(math.ceil((stop - start) / step))
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ret = [None] * count
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if not ret:
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return ret
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ret[0] = start
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for i in xrange(1, count):
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ret[i] = ret[i - 1] + step
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return ret"
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4965,"def backoff(start, stop, count=None, factor=2.0, jitter=False):
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""""""Returns a list of geometrically-increasing floating-point numbers,
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suitable for usage with `exponential backoff`_. Exactly like
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:func:`backoff_iter`, but without the ``'repeat'`` option for
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*count*. See :func:`backoff_iter` for more details.
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.. _exponential backoff: https://en.wikipedia.org/wiki/Exponential_backoff
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>>> backoff(1, 10)
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[1.0, 2.0, 4.0, 8.0, 10.0]
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""""""
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if count == 'repeat':
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raise ValueError(""'repeat' supported in backoff_iter, not backoff"")
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return list(backoff_iter(start, stop, count=count,
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factor=factor, jitter=jitter))"
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4966,"def backoff_iter(start, stop, count=None, factor=2.0, jitter=False):
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""""""Generates a sequence of geometrically-increasing floats, suitable
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for usage with `exponential backoff`_. Starts with *start*,
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increasing by *factor* until *stop* is reached, optionally
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stopping iteration once *count* numbers are yielded. *factor*
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defaults to 2. In general retrying with properly-configured
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backoff creates a better-behaved component for a larger service
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ecosystem.
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.. _exponential backoff: https://en.wikipedia.org/wiki/Exponential_backoff
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>>> list(backoff_iter(1.0, 10.0, count=5))
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[1.0, 2.0, 4.0, 8.0, 10.0]
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>>> list(backoff_iter(1.0, 10.0, count=8))
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[1.0, 2.0, 4.0, 8.0, 10.0, 10.0, 10.0, 10.0]
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>>> list(backoff_iter(0.25, 100.0, factor=10))
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[0.25, 2.5, 25.0, 100.0]
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A simplified usage example:
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.. code-block:: python
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for timeout in backoff_iter(0.25, 5.0):
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try:
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res = network_call()
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break
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except Exception as e:
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log(e)
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time.sleep(timeout)
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An enhancement for large-scale systems would be to add variation,
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or *jitter*, to timeout values. This is done to avoid a thundering
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herd on the receiving end of the network call.
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Finally, for *count*, the special value ``'repeat'`` can be passed to
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continue yielding indefinitely.
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Args:
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start (float): Positive number for baseline.
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stop (float): Positive number for maximum.
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count (int): Number of steps before stopping
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iteration. Defaults to the number of steps between *start* and
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*stop*. Pass the string, `'repeat'`, to continue iteration
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indefinitely.
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factor (float): Rate of exponential increase. Defaults to `2.0`,
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