asyncio-compatible timeout context manager.
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:
async with timeout(1.5): await inner()
- If
inner()
is executed faster than in1.5
seconds nothing happens. - Otherwise
inner()
is cancelled internally by sendingasyncio.CancelledError
into butasyncio.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.
$ pip install asyncio-timeout
The library is Python 3 only!
The module is written by Andrew Svetlov.
It's Apache 2 licensed and freely available.