python-can/can/interface.py at develop · feuerball/python-can · GitHub

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"""

This module contains the base implementation of :class:`can.BusABC` as well

as a list of all available backends and some implemented

CyclicSendTasks.

"""

import importlib

import logging

from typing import Any, cast, Iterable, Type, Optional, Union, List

from . import util

from .bus import BusABC

from .interfaces import BACKENDS

from .exceptions import CanInterfaceNotImplementedError

from .typechecking import AutoDetectedConfig, Channel

log = logging.getLogger("can.interface")

log_autodetect = log.getChild("detect_available_configs")

def _get_class_for_interface(interface: str) -> Type[BusABC]:

"""

Returns the main bus class for the given interface.

:raises:

NotImplementedError if the interface is not known

:raises CanInterfaceNotImplementedError:

if there was a problem while importing the interface or the bus class within that

"""

# Find the correct backend

try:

module_name, class_name = BACKENDS[interface]

except KeyError:

raise NotImplementedError(

f"CAN interface '{interface}' not supported"

) from None

# Import the correct interface module

try:

module = importlib.import_module(module_name)

except Exception as e:

raise CanInterfaceNotImplementedError(

f"Cannot import module {module_name} for CAN interface '{interface}': {e}"

) from None

# Get the correct class

try:

bus_class = getattr(module, class_name)

except Exception as e:

raise CanInterfaceNotImplementedError(

f"Cannot import class {class_name} from module {module_name} for CAN interface "

f"'{interface}': {e}"

) from None

return cast(Type[BusABC], bus_class)

class Bus(BusABC): # pylint: disable=abstract-method

"""Bus wrapper with configuration loading.

Instantiates a CAN Bus of the given ``interface``, falls back to reading a

configuration file from default locations.

.. note::

Please note that while the arguments provided to this class take precedence

over any existing values from configuration, it is possible that other parameters

from the configuration may be added to the bus instantiation.

This could potentially have unintended consequences. To prevent this,

you may use the *ignore_config* parameter to ignore any existing configurations.

:param channel:

Channel identification. Expected type is backend dependent.

Set to ``None`` to let it be resolved automatically from the default

:ref:`configuration`.

:param interface:

See :ref:`interface names` for a list of supported interfaces.

Set to ``None`` to let it be resolved automatically from the default

:ref:`configuration`.

:param config_context:

Extra 'context', that is passed to config sources.

This can be used to select a section other than 'default' in the configuration file.

:param ignore_config:

If ``True``, only the given arguments will be used for the bus instantiation. Existing

configuration sources will be ignored.

:param kwargs:

``interface`` specific keyword arguments.

:raises ~can.exceptions.CanInterfaceNotImplementedError:

if the ``interface`` isn't recognized or cannot be loaded

:raises ~can.exceptions.CanInitializationError:

if the bus cannot be instantiated

:raises ValueError:

if the ``channel`` could not be determined

"""

@staticmethod

@util.deprecated_args_alias(

deprecation_start="4.2.0",

deprecation_end="5.0.0",

bustype="interface",

context="config_context",

)

def __new__( # type: ignore

cls: Any,

channel: Optional[Channel] = None,

interface: Optional[str] = None,

config_context: Optional[str] = None,

ignore_config: bool = False,

**kwargs: Any,

) -> BusABC:

# figure out the rest of the configuration; this might raise an error

if interface is not None:

kwargs["interface"] = interface

if channel is not None:

kwargs["channel"] = channel

if not ignore_config:

kwargs = util.load_config(config=kwargs, context=config_context)

# resolve the bus class to use for that interface

cls = _get_class_for_interface(kwargs["interface"])

# remove the "interface" key, so it doesn't get passed to the backend

del kwargs["interface"]

# make sure the bus can handle this config format

channel = kwargs.pop("channel", channel)

if channel is None:

# Use the default channel for the backend

bus = cls(**kwargs)

else:

bus = cls(channel, **kwargs)

return cast(BusABC, bus)

def detect_available_configs(

interfaces: Union[None, str, Iterable[str]] = None

) -> List[AutoDetectedConfig]:

"""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.

:param interfaces: 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.

:rtype: list[dict]

:return: an iterable of dicts, each suitable for usage in

the constructor of :class:`can.BusABC`.

"""

# Figure out where to search

if interfaces is None:

interfaces = BACKENDS

elif isinstance(interfaces, str):

interfaces = (interfaces,)

# else it is supposed to be an iterable of strings

result = []

for interface in interfaces:

try:

bus_class = _get_class_for_interface(interface)

except CanInterfaceNotImplementedError:

log_autodetect.debug(

'interface "%s" cannot be loaded for detection of available configurations',

interface,

)

continue

# get available channels

try:

available = list(

bus_class._detect_available_configs() # pylint: disable=protected-access

)

except NotImplementedError:

log_autodetect.debug(

'interface "%s" does not support detection of available configurations',

interface,

)

else:

log_autodetect.debug(

'interface "%s" detected %i available configurations',

interface,

len(available),

)

# add the interface name to the configs if it is not already present

for config in available:

if "interface" not in config:

config["interface"] = interface

# append to result

result += available

return result

python-can/can/interface.py at develop · feuerball/python-can · GitHub

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