# pyudev.core module

Core types and functions of `pyudev`.

class pyudev.core.Context

  Bases: `object`

  A device database connection.

  This class represents a connection to the udev device database, and is really the central object to access udev. You need an instance of this class for almost anything else in pyudev.

  This class itself gives access to various udev configuration data (e.g. `sys_path`, `device_path`), and provides device enumeration (`list_devices()`).

  Instances of this class can directly be given as `udev *` to functions wrapped through `ctypes`.

  property device_path

    The device directory path defaulting to `/dev` as unicode string.

  list_devices(**kwargs)

    List all available devices.

    The arguments of this method are the same as for `Enumerator.match()`. In fact, the arguments are simply passed straight to method `match()`.

    This function creates and returns an `Enumerator` object, that can be used to filter the list of devices, and eventually retrieve `Device` objects representing matching devices.

    Changed in version 0.8: Accept keyword arguments now for easy matching.

  property log_priority

    The logging priority of the interal logging facitility of udev as integer with a standard `syslog` priority. Assign to this property to change the logging priority.

    UDev uses the standard `syslog` priorities. Constants for these priorities are defined in the `syslog` module in the standard library:

        >>> import syslog
        >>> context = pyudev.Context()
        >>> context.log_priority = syslog.LOG_DEBUG

    Added in version 0.9.

  property run_path

    The run runtime directory path defaulting to `/run` as unicode string.

    Required udev version: 167

    Added in version 0.10.

  property sys_path

    The `sysfs` mount point defaulting to `/sys'` as unicode string.

class pyudev.core.Enumerator(context)

  Bases: `object`

  A filtered iterable of devices.

  To retrieve devices, simply iterate over an instance of this class. This operation yields `Device` objects representing the available devices.

  Before iteration the device list can be filtered by subsystem or by property values using `match_subsystem()` and `match_property()`. Multiple subsystem (property) filters are combined using a logical OR, filters of different types are combined using a logical AND. The following filter for instance:

      devices.match_subsystem('block').match_property(
          'ID_TYPE', 'disk').match_property('DEVTYPE', 'disk')

  means the following:

      subsystem == 'block' and (ID_TYPE == 'disk' or DEVTYPE == 'disk')

  Once added, a filter cannot be removed anymore. Create a new object instead.

  Instances of this class can directly be given as given `udev_enumerate *` to functions wrapped through `ctypes`.

  match(**kwargs)

    Include devices according to the rules defined by the keyword arguments. These keyword arguments are interpreted as follows:

    - The value for the keyword argument `subsystem` is forwarded to `match_subsystem()`.

    - The value for the keyword argument `sys_name` is forwared to `match_sys_name()`.

    - The value for the keyword argument `tag` is forwared to `match_tag()`.

    - The value for the keyword argument `parent` is forwared to `match_parent()`.

    - All other keyword arguments are forwareded one by one to `match_property()`. The keyword argument itself is interpreted as property name, the value of the keyword argument as the property value.

    All keyword arguments are optional, calling this method without no arguments at all is simply a noop.

    Return the instance again.

    Added in version 0.8.

    Changed in version 0.13: Add `parent` keyword.

  match_attribute(attribute, value, nomatch=False)

    Include all devices, whose `attribute` has the given `value`.

    `attribute` is either a unicode string or a byte string, containing the name of a sys attribute to match. `value` is an attribute value, being one of the following types:

    - `int()`,

    - `bool()`

    - A byte string

    - Anything convertable to a unicode string (including a unicode string itself)

    If `nomatch` is `True` (default is `False`), the match is inverted: A device is include if the `attribute` does not match the given `value`.

    Note

    If `nomatch` is `True`, devices which do not have the given `attribute` at all are also included. In other words, with `nomatch=True` the given `attribute` is not guaranteed to exist on all returned devices.

    Return the instance again.

  match_is_initialized()

    Include only devices, which are initialized.

    Initialized devices have properly set device node permissions and context, and are (in case of network devices) fully renamed.

    Currently this will not affect devices which do not have device nodes and are not network interfaces.

    Return the instance again.

    See also

    `Device.is_initialized`

    Required udev version: 165

    Added in version 0.8.

  match_parent(parent)

    Include all devices on the subtree of the given `parent` device.

    The `parent` device itself is also included.

    `parent` is a `Device`.

    Return the instance again.

    Required udev version: 172

    Added in version 0.13.

  match_property(prop, value)

    Include all devices, whose `prop` has the given `value`.

    `prop` is either a unicode string or a byte string, containing the name of the property to match. `value` is a property value, being one of the following types:

    - `int()`

    - `bool()`

    - A byte string

    - Anything convertable to a unicode string (including a unicode string itself)

    Return the instance again.

  match_subsystem(subsystem, nomatch=False)

    Include all devices, which are part of the given `subsystem`.

    `subsystem` is either a unicode string or a byte string, containing the name of the subsystem. If `nomatch` is `True` (default is `False`), the match is inverted: A device is only included if it is not part of the given `subsystem`.

    Note that, if a device has no subsystem, it is not included either with value of `nomatch` True or with value of `nomatch` False.

    Return the instance again.

  match_sys_name(sys_name)

    Include all devices with the given name.

    `sys_name` is a byte or unicode string containing the device name.

    Return the instance again.

    Added in version 0.8.

  match_tag(tag)

    Include all devices, which have the given `tag` attached.

    `tag` is a byte or unicode string containing the tag name.

    Return the instance again.

    Required udev version: 154

    Added in version 0.6.