.. currentmodule:: asyncio

.. _asyncio-exceptions:

========== Exceptions

.. exception:: TimeoutError

The operation has exceeded the given deadline.

.. important:: This exception is different from the builtin :exc:TimeoutError exception.

.. exception:: CancelledError

The operation has been cancelled.

This exception can be caught to perform custom operations when asyncio Tasks are cancelled. In almost all situations the exception must be re-raised.

.. important::

  This exception is a subclass of :exc:`Exception`, so it can be
  accidentally suppressed by an overly broad ``try..except`` block::

    try:
        await operation
    except Exception:
        # The cancellation is broken because the *except* block
        # suppresses the CancelledError exception.
        log.log('an error has occurred')

  Instead, the following pattern should be used::

    try:
        await operation
    except asyncio.CancelledError:
        raise
    except Exception:
        log.log('an error has occurred')

.. exception:: InvalidStateError

Invalid internal state of :class:Task or :class:Future.

Can be raised in situations like setting a result value for a Future object that already has a result value set.

.. exception:: SendfileNotAvailableError

The "sendfile" syscall is not available for the given socket or file type.

A subclass of :exc:RuntimeError.

.. exception:: IncompleteReadError

The requested read operation did not complete fully.

Raised by the :ref:asyncio stream APIs<asyncio-streams>.

This exception is a subclass of :exc:EOFError.

.. attribute:: expected

  The total number (:class:`int`) of expected bytes.

.. attribute:: partial

  A string of :class:`bytes` read before the end of stream was reached.

.. exception:: LimitOverrunError

Reached the buffer size limit while looking for a separator.

Raised by the :ref:asyncio stream APIs <asyncio-streams>.

.. attribute:: consumed

  The total number of to be consumed bytes.