Context – the central object

class pyudev.Context

The udev context.

This is the central object to access udev. An instance of this class must be created before anything else can be done. It holds the udev configuration and provides the interface to list devices (see list_devices()).

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

__init__()

Create a new context.

sys_path

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

The mount point can be overwritten using the environment variable SYSFS_PATH. Use this for testing purposes.

device_path

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

This can be overridden in the udev configuration.

run_path

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

Required udev version: 167

New in version 0.10.

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

New in version 0.9.

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

class pyudev.Enumerator

Enumerate all available 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.

New in version 0.8.

Changed in version 0.13: Added parent keyword

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.

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.

New in version 0.8.

match_property(property, value)

Include all devices, whose property has the given value.

property 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_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_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

New in version 0.6.

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

New in version 0.13.

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

New in version 0.8.

__iter__()

Iterate over all matching devices.

Yield Device objects.