Library API¶
The main objects are the BusABC
and the Message
.
A form of CAN interface is also required.
Hint
Check the backend specific documentation for any implementation specific details.
Utilities¶
- can.detect_available_configs(interfaces=None)[source]¶
Detect all configurations/channels that the interfaces could currently connect with.
This might be quite time consuming.
Automated configuration detection may not be implemented by every interface on every platform. This method will not raise an error in that case, but with rather return an empty list for that interface.
- Parameters
interfaces (
Union
[None
,str
,Iterable
[str
]]) – either - the name of an interface to be searched in as a string, - an iterable of interface names to search in, or - None to search in all known interfaces.- Return type
- Returns
an iterable of dicts, each suitable for usage in the constructor of
can.BusABC
.
Notifier¶
The Notifier object is used as a message distributor for a bus. Notifier creates a thread to read messages from the bus and distributes them to listeners.
- class can.Notifier(bus, listeners, timeout=1.0, loop=None)[source]¶
Manages the distribution of
Message
instances to listeners.Supports multiple buses and listeners.
Note
Remember to call stop() after all messages are received as many listeners carry out flush operations to persist data.
- Parameters
bus (
Union
[BusABC
,List
[BusABC
]]) – A Bus or a list of buses to listen to.listeners (
Iterable
[Union
[Listener
,Callable
[[Message
],None
]]]) – An iterable ofListener
or callables that receive aMessage
and return nothing.timeout (
float
) – An optional maximum number of seconds to wait for anyMessage
.loop (
Optional
[AbstractEventLoop
]) – Anasyncio
event loop to schedule thelisteners
in.
- add_listener(listener)[source]¶
Add new Listener to the notification list. If it is already present, it will be called two times each time a message arrives.
- remove_listener(listener)[source]¶
Remove a listener from the notification list. This method throws an exception if the given listener is not part of the stored listeners.
- Parameters
listener (
Listener
) – Listener to be removed from the list to be notified- Raises
ValueError – if listener was never added to this notifier
- Return type
Errors¶
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 ...'
- 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
can.CanInterfaceNotImplementedError
is raised instead. If initialization fails due to a value being out of range, aValueError
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
- 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
- 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
- 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