async-timeout

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.

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.