Source code: Lib/asyncio/exceptions.py

exception asyncio.TimeoutError

A deprecated alias of TimeoutError, raised when the operation has exceeded the given deadline.

Changed in version 3.11: This class was made an alias of TimeoutError.

exception asyncio.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.

Changed in version 3.8: CancelledError is now a subclass of BaseException rather than Exception.

exception asyncio.InvalidStateError

Invalid internal state of Task or Future.

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

exception asyncio.SendfileNotAvailableError

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

A subclass of RuntimeError.

exception asyncio.IncompleteReadError

The requested read operation did not complete fully.

Raised by the asyncio stream APIs.

This exception is a subclass of EOFError.


The total number (int) of expected bytes.


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

exception asyncio.LimitOverrunError

Reached the buffer size limit while looking for a separator.

Raised by the asyncio stream APIs.


The total number of to be consumed bytes.