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