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.