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async-timeout
=============
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asyncio-compatible timeout context manager.
DEPRECATED
----------
This library has effectively been upstreamed into Python 3.11+.
Therefore this library is considered deprecated and no longer actively
supported.
Version 5.0+ provides dual-mode when executed on Python 3.11+:
``asyncio_timeout.Timeout is fully compatible with asyncio.Timeout`` *and*
old
versions of the library.
Anyway, using upstream is highly recommended. asyncio_timeout exists only
for the
sake of backward compatibility, easy supporting both old and new Python by
the same
code, and easy misgration.
If rescheduling API is not important and only ``async with timeout(...):
...`` functionality is required,
a user could apply conditional import::
if sys.version_info >= (3, 11):
from asyncio import timeout, timeout_at
else:
from async_timeout import timeout, timeout_at
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()`` / ``.expired`` for check if timeout
happens
exactly in context manager::
async with timeout(1.5) as cm:
await inner()
print(cm.expired()) # recommended api
print(cm.expired) # compatible api
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 ``.when()`` / ``.deadline``::
async with timeout(1.5) as cm:
cm.when() # recommended api
cm.deadline # compatible api
Not finished yet timeout can be rescheduled by ``shift()
or update()`` methods::
async with timeout(1.5) as cm:
# recommended api
cm.reschedule(cm.when() + 1) # add another second on waiting
# compatible api
cm.shift(1) # add another second on waiting
cm.update(loop.time() + 5) # reschedule to now+5 seconds
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