Error Handling#

There are several specific Exception classes to allow user code to react to specific scenarios related to CAN busses:

Exception (Python standard library)
 +-- ...
 +-- CanError (python-can)
     +-- CanInterfaceNotImplementedError
     +-- CanInitializationError
     +-- CanOperationError
     +-- CanTimeoutError

Keep in mind that some functions and methods may raise different exceptions. For example, validating typical arguments and parameters might result in a ValueError. This should always be documented for the function at hand.

exception can.exceptions.CanError(message='', error_code=None)[source]#

Bases: Exception

Base class for all CAN related exceptions.

If specified, the error code is automatically appended to the message:

>>> # With an error code (it also works with a specific error):
>>> error = CanOperationError(message="Failed to do the thing", error_code=42)
>>> str(error)
'Failed to do the thing [Error Code 42]'
>>>
>>> # Missing the error code:
>>> plain_error = CanError(message="Something went wrong ...")
>>> str(plain_error)
'Something went wrong ...'
Parameters

  • error_code (Optional[int]) – An optional error code to narrow down the cause of the fault

  • error_code – An optional error code to narrow down the cause of the fault

  • message (str) –

Return type

None

exception can.exceptions.CanInitializationError(message='', error_code=None)[source]#

Bases: can.exceptions.CanError

Indicates an error the occurred while initializing a can.BusABC.

If initialization fails due to a driver or platform missing/being unsupported, a CanInterfaceNotImplementedError is raised instead. If initialization fails due to a value being out of range, a ValueError is raised.

Example scenarios:

  • Try to open a non-existent device and/or channel

  • Try to use an invalid setting, which is ok by value, but not ok for the interface

  • The device or other resources are already used

Parameters
Return type

None

exception can.exceptions.CanInterfaceNotImplementedError(message='', error_code=None)[source]#

Bases: can.exceptions.CanError, NotImplementedError

Indicates that the interface is not supported on the current platform.

Example scenarios:

  • No interface with that name exists

  • The interface is unsupported on the current operating system or interpreter

  • The driver could not be found or has the wrong version

Parameters
Return type

None

exception can.exceptions.CanOperationError(message='', error_code=None)[source]#

Bases: can.exceptions.CanError

Indicates an error while in operation.

Example scenarios:

  • A call to a library function results in an unexpected return value

  • An invalid message was received

  • The driver rejected a message that was meant to be sent

  • Cyclic redundancy check (CRC) failed

  • A message remained unacknowledged

  • A buffer is full

Parameters
Return type

None

exception can.exceptions.CanTimeoutError(message='', error_code=None)[source]#

Bases: can.exceptions.CanError, TimeoutError

Indicates the timeout of an operation.

Example scenarios:

  • Some message could not be sent after the timeout elapsed

  • No message was read within the given time

Parameters
Return type

None

can.exceptions.error_check(error_message=None, exception_type=<class 'can.exceptions.CanOperationError'>)[source]#

Catches any exceptions and turns them into the new type while preserving the stack trace.

Parameters
Return type

collections.abc.Generator[None, None, None]