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async-timeout |
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============= |
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.. image:: https: |
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:alt: Chat on Gitter |
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asyncio-compatible timeout context manager. |
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Usage example |
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------------- |
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The context manager is useful in cases when you want to apply timeout |
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logic around block of code or in cases when ``asyncio.wait_for()`` is |
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not suitable. Also it's much faster than ``asyncio.wait_for()`` |
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because ``timeout`` doesn't create a new task. |
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The ``timeout(delay, *, loop=None)`` call returns a context manager |
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that cancels a block on *timeout* expiring:: |
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from async_timeout import timeout |
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async with timeout(1.5): |
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await inner() |
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1. If ``inner()`` is executed faster than in ``1.5`` seconds nothing |
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happens. |
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2. Otherwise ``inner()`` is cancelled internally by sending |
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``asyncio.CancelledError`` into but ``asyncio.TimeoutError`` is |
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raised outside of context manager scope. |
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*timeout* parameter could be ``None`` for skipping timeout functionality. |
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Alternatively, ``timeout_at(when)`` can be used for scheduling |
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at the absolute time:: |
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loop = asyncio.get_event_loop() |
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now = loop.time() |
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async with timeout_at(now + 1.5): |
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await inner() |
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Please note: it is not POSIX time but a time with |
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undefined starting base, e.g. the time of the system power on. |
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Context manager has ``.expired`` property for check if timeout happens |
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exactly in context manager:: |
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async with timeout(1.5) as cm: |
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await inner() |
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print(cm.expired) |
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The property is ``True`` if ``inner()`` execution is cancelled by |
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timeout context manager. |
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If ``inner()`` call explicitly raises ``TimeoutError`` ``cm.expired`` |
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is ``False``. |
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The scheduled deadline time is available as ``.deadline`` property:: |
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async with timeout(1.5) as cm: |
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cm.deadline |
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Not finished yet timeout can be rescheduled by ``shift_by()`` |
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or ``shift_to()`` methods:: |
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async with timeout(1.5) as cm: |
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cm.shift(1) # add another second on waiting |
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cm.update(loop.time() + 5) # reschedule to now+5 seconds |
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Rescheduling is forbidden if the timeout is expired or after exit from ``async with`` |
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code block. |
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Installation |
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------------ |
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:: |
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$ pip install async-timeout |
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The library is Python 3 only! |
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Authors and License |
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------------------- |
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The module is written by Andrew Svetlov. |
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It's *Apache 2* licensed and freely available. |
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