pyudev.discover module

Tools to discover a device given limited information.

class pyudev.discover.DeviceFileHypothesis

Bases: pyudev.discover.Hypothesis

Discover the device assuming the value is some portion of a device file.

The device file may be a link to a device node.

Get all directories that may contain links to device nodes.

This method checks the device links of every device, so it is very expensive.

Parameters

context (Context) – the context

Returns

a sorted list of directories that contain device links

Return type

list

classmethod lookup(context, key)

Lookup the device under the assumption that the key is part of the name of a device file.

Parameters

  • context (Context) – the context

  • key (str) – a portion of the device file name

It is assumed that either it is the whole name of the device file or it is the basename.

A device file may be a device node or a device link.

classmethod match(value)

Match the given string according to the hypothesis.

The purpose of this method is to obtain a value corresponding to value if that is possible. It may use a regular expression, but in general it should just return value and let the lookup method sort out the rest.

Parameters

value (str) – the string to inspect

Returns

the matched thing or None if unmatched

Return type

the type of lookup’s key parameter or NoneType

classmethod setup(context)

Set the link directories to be used when discovering by file.

Uses get_link_dirs, so is as expensive as it is.

Parameters

context (Context) – the context

class pyudev.discover.DeviceNameHypothesis

Bases: pyudev.discover.Hypothesis

Discover the device assuming the input is a device name.

Try every available subsystem.

classmethod find_subsystems(context)

Find all subsystems in sysfs.

Parameters

context (Context) – the context

Return type

frozenset

Returns

subsystems in sysfs

classmethod lookup(context, key)

Lookup by the path.

Parameters

  • context (Context) – the context

  • key (str) – the device path

Returns

a list of matching devices

Return type

frozenset of Device

classmethod match(value)

Match value under the assumption that it is a device name.

Returns

the device path or None

Return type

str or NoneType

class pyudev.discover.DeviceNumberHypothesis

Bases: pyudev.discover.Hypothesis

Represents the hypothesis that the device is a device number.

The device may be separated into major/minor number or a composite number.

classmethod find_subsystems(context)

Find subsystems in /sys/dev.

Parameters

context (Context) – the context

Returns

a lis of available subsystems

Return type

list of str

classmethod lookup(context, key)

Lookup by the device number.

Parameters

  • context (Context) – the context

  • key (int) – the device number

Returns

a list of matching devices

Return type

frozenset of Device

classmethod match(value)

Match the number under the assumption that it is a device number.

Returns

the device number or None

Return type

int or NoneType

class pyudev.discover.DevicePathHypothesis

Bases: pyudev.discover.Hypothesis

Discover the device assuming the identifier is a device path.

classmethod lookup(context, key)

Lookup by the path.

Parameters

  • context (Context) – the context

  • key (str) – the device path

Returns

a list of matching devices

Return type

frozenset of Device

classmethod match(value)

Match value under the assumption that it is a device path.

Returns

the device path or None

Return type

str or NoneType

class pyudev.discover.Discovery

Bases: object

Provides discovery methods for devices.

get_devices(context, value)

Get the devices corresponding to value.

Parameters

  • context (Context) – the context

  • value (str) – some identifier of the device

Returns

a list of corresponding devices

Return type

frozenset of Device

setup(context)

Set up individual hypotheses.

May be an expensive call.

Parameters

context (Context) – the context

class pyudev.discover.Hypothesis

Bases: object

Represents a hypothesis about the meaning of the device identifier.

classmethod get_devices(context, value)

Get any devices that may correspond to the given string.

Parameters

  • context (Context) – the pyudev context

  • value (str) – the value to look for

Returns

a list of devices obtained

Return type

set of Device

abstract classmethod lookup(context, key)

Lookup the given string according to the hypothesis.

Parameters

  • context (Context) – the pyudev context

  • key (the type of match's return value if not None) – a key with which to lookup the device

Returns

a list of Devices obtained

Return type

frozenset of Device

abstract classmethod match(value)

Match the given string according to the hypothesis.

The purpose of this method is to obtain a value corresponding to value if that is possible. It may use a regular expression, but in general it should just return value and let the lookup method sort out the rest.

Parameters

value (str) – the string to inspect

Returns

the matched thing or None if unmatched

Return type

the type of lookup’s key parameter or NoneType

classmethod setup(context)

A potentially expensive method that may allow an Hypothesis to find devices more rapidly or to find a device that it would otherwise miss.

Parameters

context (Context) – the pyudev context

pyudev.discover.wrap_exception(func)

Allow Device discovery methods to return None instead of raising an exception.