Scroll to navigation

DASBUS(1) dasbus DASBUS(1)

NAME

dasbus - dasbus

Dasbus is a DBus library written in Python 3, based on GLib and inspired by pydbus. The code used to be part of the Anaconda Installer project. It was based on the pydbus library, but we replaced it with our own solution because its upstream development stalled. The dasbus library is a result of this effort.

REQUIREMENTS

  • Python 3.6+
  • PyGObject 3

You can install PyGObject provided by your operating system or use PyPI. The system package is usually called python3-gi, python3-gobject or pygobject3. See the instructions for your platform (only for PyGObject, you don't need cairo or GTK).

The library is known to work with Python 3.8, PyGObject 3.34 and GLib 2.63, but these are not the required minimal versions.

INSTALLATION

Install the package from PyPI or install the package provided by your operating system if available.

Install from PyPI

Follow the instructions above to install the requirements before you install dasbus with pip. The required dependencies has to be installed manually in this case.

pip3 install dasbus


Install on Arch Linux

Build and install the community package from the Arch User Repository. Follow the guidelines.

git clone https://aur.archlinux.org/python-dasbus.git
cd python-dasbus
makepkg -si


Install on Debian / Ubuntu

Install the system package on Debian 11+ or Ubuntu 22.04+.

sudo apt install python3-dasbus


Install on Fedora / CentOS / RHEL

Install the system package on Fedora 31+, CentOS Stream 8+ or RHEL 8+.

sudo dnf install python3-dasbus


Install on openSUSE

Install the system package on openSUSE Tumbleweed or openSUSE Leap 15.2+.

sudo zypper install python3-dasbus


Development and testing

Install podman and use the following command to run all tests in a container. It doesn't require any additional dependencies:

make container-ci


Use the command below to run only the unit tests:

make container-ci CI_CMD="make test"


dasbus vs pydbus

The dasbus library used to be based on pydbus, but it was later reimplemented. We have changed the API and the implementation of the library based on our experience with pydbus. However, it should be possible to modify dasbus classes to work the same way as pydbus classes.

What is new

  • Support for asynchronous DBus calls: DBus methods can be called asynchronously.
  • Support for Unix file descriptors: It is possible to send or receive Unix file descriptors.
  • Mapping DBus errors to exceptions: Use Python exceptions to propagate and handle DBus errors. Define your own rules for mapping errors to exceptions and back. See the ErrorMapper class
  • Support for type hints: Use Python type hints from dasbus.typing to define DBus types.
  • Generating XML specifications: Automatically generate XML specifications from Python classes with the dbus_interface decorator.
  • Support for DBus structures: Represent DBus structures (dictionaries of variants) by Python objects. See the DBusData class.
  • Support for groups of DBus objects: Use DBus containers from dasbus.server.container to publish groups of Python objects.
  • Composition over inheritance: The library follows the principle of composition over inheritance. It allows to easily change the default behaviour.
  • Lazy DBus connections: DBus connections are established on demand.
  • Lazy DBus proxies: Attributes of DBus proxies are created on demand.

What is different

  • No context managers: There are no context managers in dasbus. Context managers and event loops don't work very well together.
  • No auto-completion: There is no support for automatic completion of DBus names and paths. We recommend to work with constants defined by classes from dasbus.identifier instead of strings.
  • No unpacking of variants: The dasbus library doesn't unpack variants by default. It means that values received from DBus match the types declared in the XML specification. Use the get_native function to unpack the values.
  • Obtaining proxy objects: Call the get_proxy method to get a proxy of the specified DBus object.
  • No single-interface view: DBus proxies don't support single-interface views. Use the InterfaceProxy class to access a specific interface of a DBus object.
  • Higher priority of standard interfaces: If there is a DBus interface in the XML specification that redefines a member of a standard interface, the DBus proxy will choose a member of the standard interface. Use the InterfaceProxy class to access a specific interface of a DBus object.
  • No support for help: Members of DBus proxies are created lazily, so the build-in help function doesn't return useful information about the DBus interfaces.
  • Watching DBus names: Use a service observer to watch a DBus name.
  • Acquiring DBus names: Call the register_service method to acquire a DBus name.
  • Providing XML specifications: Use the __dbus_xml__ attribute to provide the XML specification of a DBus object. Or you can generate it from the code using the dbus_interface decorator.
  • No support for polkit: There is no support for the DBus service org.freedesktop.PolicyKit1.

What is the same (for now)

  • No support for other event loops: Dasbus uses GLib as its backend, so it requires to use the GLib event loop. However, the GLib part of dasbus is separated from the rest of the code, so it shouldn't be too difficult to add support for a different backend. It would be necessary to replace dasbus.typing.Variant and dasbus.typing.VariantType with their abstractions and reorganize the code.
  • No support for org.freedesktop.DBus.ObjectManager: There is no support for object managers, however the DBus containers could be a good starting point.

Public API

dasbus.client package

dasbus.client.handler module

Bases: object

The abstract handler of a remote DBus object.

Create a member of the DBus object.
  • interface_name -- a name of the interface
  • member_name -- a name of the member

a signal, a method or a property


Disconnect members of the DBus object.

Unsubscribe from DBus signals and disconnect all registered callbacks of the proxy signals.


DBus object path.
a DBus path


DBus service name.
a DBus name


DBus specification.


Bases: dasbus.client.handler.AbstractClientObjectHandler

The client handler of a DBus object.

Disconnect members of the DBus object.


Bases: object

The low-level DBus client library based on GLib.


Asynchronously call a DBus method.

Get a message of the remote DBus error.

Get a DBus name of the remote DBus error.

Is it a remote DBus error?

Is it a timeout error?

Subscribe to a signal.
a callback to unsubscribe


Synchronously call a DBus method.
a result of the DBus call



dasbus.client.observer module

Bases: object

Base class for DBus observers.

This class is recommended to use only to watch the availability of a service on DBus. It doesn't provide any support for accessing objects provided by the service.

Usage:

# Create the observer and connect to its signals.
observer = DBusObserver(SystemBus, "org.freedesktop.NetworkManager")
def callback1(observer):


    print("Service is available!")
def callback2(observer):


    print("Service is unavailable!")
observer.service_available.connect(callback1)
observer.service_unavailable.connect(callback2)
# Connect to the service once it is available.
observer.connect_once_available()
# Disconnect the observer.
observer.disconnect()


Connect to the service once it is available.

The observer is not connected to the service until it emits the service_available signal.


Disconnect from the service.

Disconnect from the service if it is connected and stop watching its availability.


The proxy can be accessed.

Signal that emits when the service is available.

Signal emits this class as an argument. You have to call the watch method to activate the signals.


Returns a DBus name.

Signal that emits when the service is unavailable.

Signal emits this class as an argument. You have to call the watch method to activate the signals.



Bases: Exception

Exception class for the DBus observers.


Bases: object

The low-level DBus monitoring library based on GLib.

Watch a service name on the DBus connection.


dasbus.client.property module

Bases: object

Proxy of a remote DBus property.

It can be used to define instance attributes.

Get the value of the DBus property.

Set the value of the DBus property.


dasbus.client.proxy module

Bases: object

Abstract proxy of a remote DBus object.


Bases: dasbus.client.proxy.AbstractObjectProxy

Proxy of a remote DBus interface.


Bases: dasbus.client.proxy.AbstractObjectProxy

Proxy of a remote DBus object.


Disconnect the DBus proxy from the remote object.
proxy -- a DBus proxy


Get an object path of the remote DBus object.
proxy -- a DBus proxy
a DBus path


dasbus.server package

dasbus.server.container module

Bases: object

The container of DBus objects.

A DBus container should be used to dynamically publish Publishable objects within the same namespace. It generates a unique DBus path for each object. It is able to resolve a DBus path into an object and an object into a DBus path.

Example:

# Create a container of tasks.
container = DBusContainer(


    namespace=("my", "project"),


    basename="Task",


    message_bus=DBus
)
# Publish a task.
path = container.to_object_path(MyTask())
# Resolve an object path into a task.
task = container.from_object_path(path)


Convert a DBus path to a published object.

If no published object is found for the given DBus path, raise DBusContainerError.

object_path -- a DBus path
a published object


Convert DBus paths to published objects.
object_paths -- a list of DBus paths
a list of published objects


Set the namespace.

All DBus objects from the container should use the same namespace, so the namespace should be set up before any of the DBus objects are published.

namespace -- a sequence of names


Convert a publishable object to a DBus path.

If no DBus path is found for the given object, publish the object on the container message bus with a unique DBus path generated from the container namespace.

obj -- a publishable object
a DBus path


Convert publishable objects to DBus paths.
objects -- a list of publishable objects
a list of DBus paths



Bases: Exception

General exception for DBus container errors.


dasbus.server.handler module

Bases: object

The abstract handler of a published object.

Connect the object to DBus.

Handle emitted signals of the object with the _emit_signal method and handle incoming DBus calls with the _handle_call method.


Disconnect the object from DBus.

Unregister the object and disconnect all signals.


DBus specification.


Bases: object

The low-level DBus server library based on GLib.

Emit a DBus signal.

Get information about the DBus call.

Supported items:

sender str: The bus name that invoked the method


There can be more supported items in the future.

invocation -- an invocation of a DBus call
a dictionary of information about the DBus call


Register an object on DBus.

Set the error of the DBus call.
  • invocation -- an invocation of a DBus call
  • error_name -- a DBus name of the error
  • error_message -- an error message



Set the reply of the DBus call.
  • invocation -- an invocation of a DBus call
  • out_type -- a type of the reply
  • out_value -- a value of the reply




Bases: dasbus.server.handler.AbstractServerObjectHandler

The handler of an object published on DBus.

Connect the object to DBus.

Disconnect the object from DBus.


dasbus.server.interface module

Decorator for accepting extra arguments in a DBus method.

The decorator allows the server object handler to propagate additional information about the DBus call into the decorated method.

Use a dictionary of keyword arguments:

@accepts_additional_arguments
def Method(x: Int, y: Str, **info):


    pass


Or use keyword only parameters:

@accepts_additional_arguments
def Method(x: Int, y: Str, *, call_info):


    pass


At this moment, the library provides only the call_info argument generated by GLibServer.get_call_info, but the additional arguments can be customized in the _get_additional_arguments method of the server object handler.

method -- a DBus method
a DBus method with a flag


Does the given DBus method accept additional arguments?
method -- a DBus method
True or False


DBus class.

A new DBus class can be defined as:

@dbus_class
class Class(Interface):


    ...


DBus class can implement DBus interfaces, but it cannot define a new interface.

The DBus XML specification will be generated from implemented interfaces (inherited) and it will be accessible as:

Class.__dbus_xml__



DBus interface.

A new DBus interface can be defined as:

@dbus_interface
class Interface():


    ...


The interface will be generated from the given class cls with a name interface_name and added to the DBus XML specification of the class.

The XML specification is accessible as: .. code-block:: python

Interface.__dbus_xml__


It is conventional for member names on DBus to consist of capitalized words with no punctuation. The generator of the XML specification enforces this convention to prevent unintended changes in the specification. You can provide the XML specification yourself, or override the generator class to work around these constraints.

  • interface_name -- a DBus name of the interface
  • namespace -- a sequence of strings



Bases: object

DBus signal.

Can be used as:

Signal = dbus_signal()


Or as a method decorator:

@dbus_signal
def Signal(x: Int, y: Double):


    pass


Signal is defined by the type hints of a decorated method. This method is accessible as: signal.definition

If the signal is not defined by a method, it is expected to have no arguments and signal.definition is equal to None.


Return XML specification of an object.
obj -- an object decorated with @dbus_interface or @dbus_class
a string with XML specification


dasbus.server.property module

Bases: Exception

Exception for DBus properties.


Bases: object

Standard DBus interface org.freedesktop.DBus.Properties.

DBus objects don't have to inherit this class, because the DBus library provides support for this interface by default. This class only extends this support.

Report the changed property:

self.report_changed_property('X')


Emit all changes when the method is done:

@emits_properties_changed
def SetX(x: Int):


    self.set_x(x)


DBus signal.

Can be used as:

Signal = dbus_signal()


Or as a method decorator:

@dbus_signal
def Signal(x: Int, y: Double):


    pass


Signal is defined by the type hints of a decorated method. This method is accessible as: signal.definition

If the signal is not defined by a method, it is expected to have no arguments and signal.definition is equal to None.


Flush properties changes.

Reports changed DBus property.
property_name -- a name of a DBus property



Decorator for emitting properties changes.

The decorated method has to be a member of a class that inherits PropertiesInterface.

method -- a DBus method of a class that inherits PropertiesInterface
a wrapper of a DBus method that emits PropertiesChanged


dasbus.server.publishable module

Bases: object

Abstract class for Python objects that can be published on DBus.

Example:

# Define a publishable class.
class MyObject(Publishable):


    def for_publication(self):


        return MyDBusInterface(self)
# Create a publishable object.
my_object = MyObject()
# Publish the object on DBus.
DBus.publish_object("/org/project/x", my_object.for_publication())


Return a DBus representation of this object.
an instance of @dbus_interface or @dbus_class



dasbus.server.template module

Bases: object

Basic template for a DBus interface.

This template uses a software design pattern called proxy.

This class provides a recommended way how to define DBus interfaces and create publishable DBus objects. The class that defines a DBus interface should inherit this class and be decorated with @dbus_class or @dbus_interface decorator. The implementation of this interface will be provided by a separate object called implementation. Therefore the methods of this class should call the methods of the implementation, the signals should be connected to the signals of the implementation and the getters and setters of properties should access the properties of the implementation.

@dbus_interface("org.myproject.X")
class InterfaceX(BasicInterfaceTemplate):


    def DoSomething(self) -> Str:


        return self.implementation.do_something()
class X(object):


    def do_something(self):


        return "Done!"
x = X()
i = InterfaceX(x)
DBus.publish_object("/org/myproject/X", i)


Interconnect the signals.

You should connect the emit methods of the interface signals to the signals of the implementation. Every time the implementation emits a signal, this interface reemits the signal on DBus.


Return the implementation of this interface.
an implementation



Bases: dasbus.server.template.BasicInterfaceTemplate, dasbus.server.property.PropertiesInterface

Template for a DBus interface.

The interface provides the support for the standard interface org.freedesktop.DBus.Properties.

Usage:

def connect_signals(self):


    super().connect_signals()


    self.implementation.module_properties_changed.connect(


        self.flush_changes


    )


    self.watch_property("X", self.implementation.x_changed)
@property
def X(self, x) -> Int:


    return self.implementation.x
@emits_properties_changed
def SetX(self, x: Int):


    self.implementation.set_x(x)


Watch a DBus property.

Report a change when the property is changed.

  • property_name -- a name of a DBus property
  • signal -- a signal that emits when the property is changed




dasbus.connection module

Bases: dasbus.connection.MessageBus

Representation of a connection for the specified address.

The bus address.


Bases: object

The low-level DBus connection library based on GLib.


Get a connection to a bus at the specified address.

Get a session bus connection.

Get a system bus connection.


Bases: dasbus.connection.AbstractMessageBus

Representation of a message bus based on D-Bus.

The DBus connection.

Disconnect from DBus.

Returns a proxy of a remote DBus object.

If the proxy factory is not specified, we will use a default one. If the interface name is set, we will choose InterfaceProxy, otherwise ObjectProxy.

If the interface name is set, we will add it to the additional arguments for the proxy factory.

  • service_name -- a DBus name of a service
  • object_path -- a DBus path of an object
  • interface_name -- a DBus name of an interface or None
  • proxy_factory -- a factory of a DBus object proxy
  • proxy_arguments -- additional arguments for the proxy factory

a proxy object


The proxy of DBus.

Publish an object on DBus.
  • object_path -- a DBus path of an object
  • obj -- an instance of @dbus_interface or @dbus_class
  • server_factory -- a factory of a DBus server object handler
  • server_arguments -- additional arguments for the server factory



Register a service on DBus.
  • service_name -- a DBus name of a service
  • flags -- the flags argument of the RequestName DBus method






Bases: dasbus.connection.MessageBus

Representation of a session bus connection.


Bases: dasbus.connection.MessageBus

Representation of a system bus connection.


dasbus.constants module

dasbus.error module

Bases: object

Abstract rule for mapping a Python exception to a DBus error.

Get a DBus name for the given exception type.
exception_type -- a type of the Python error
a name of the DBus error


Get an exception type of the given DBus error.

param error_name: a name of the DBus error :return: a type of the Python error


Is this rule matching the given DBus error?
error_name -- a name of the DBus error
True or False


Is this rule matching the given exception type?
exception_type -- a type of the Python error
True or False



Bases: Exception

A default DBus error.


Bases: dasbus.error.AbstractErrorRule

Default rule for mapping a Python exception to a DBus error.

Get a DBus name for the given exception type.

Get an exception type of the given DBus error.

Is this rule matching the given DBus error?

Is this rule matching the given exception type?


Bases: object

Class for mapping Python exceptions to DBus errors.

Add a rule to the error mapper.

The new rule will have a higher priority than the rules already contained in the error mapper.

rule (an instance of AbstractErrorRule) -- an error rule


Get a DBus name of the Python exception.

Try to find a matching rule in the error mapper. If a rule matches the given exception type, use the rule to get the name of the DBus error.

The rules in the error mapper are processed in the reversed order to respect the priority of the rules.

exception_type (a subclass of Exception) -- a type of the Python error
a name of the DBus error
LookupError -- if no name is found


Get a Python exception type of the DBus error.

Try to find a matching rule in the error mapper. If a rule matches the given name of a DBus error, use the rule to get the type of a Python exception.

The rules in the error mapper are processed in the reversed order to respect the priority of the rules.

error_name -- a name of the DBus error
a type of the Python exception
a subclass of Exception
LookupError -- if no type is found


Reset rules in the error mapper.

Reset the error rules to the initial state. All rules will be replaced with the default ones.



Bases: dasbus.error.AbstractErrorRule

Rule for mapping a Python exception to a DBus error.

Get a DBus name for the given exception type.

Get an exception type of the given DBus error.

Is this rule matching the given DBus error?

Is this rule matching the given exception type?


Generate a decorator for DBus errors.

Create a function for decorating Python exception classes. The decorator will add a new rule to the given error mapper that will map the class to the specified error name.

Definition of the decorator:

decorator(error_name, namespace=())


The decorator accepts a name of the DBus error and optionally a namespace of the DBus name. The namespace will be used as a prefix of the DBus name.

Usage:

# Create an error mapper.
error_mapper = ErrorMapper()
# Create a decorator for DBus errors and use it to map
# the class ExampleError to the name my.example.Error.
dbus_error = create_error_decorator(error_mapper)
@dbus_error("my.example.Error")
class ExampleError(DBusError):


    pass


error_mapper -- an error mapper
a decorator


dasbus.identifier module

Bases: dasbus.identifier.DBusBaseIdentifier

Identifier of a DBus interface.

Full name of the DBus interface.


Bases: dasbus.identifier.DBusInterfaceIdentifier

Identifier of a DBus object.

Full path of the DBus object.


Bases: dasbus.identifier.DBusObjectIdentifier

Identifier of a DBus service.

Returns a proxy of the DBus object.

If no object path is specified, we will use the object path of this DBus service.

If no interface name is specified, we will use none and create a proxy from all interfaces of the DBus object.

  • object_path -- an object identifier or a DBus path or None
  • interface_name -- an interface identifier or a DBus name or None
  • bus_arguments -- additional arguments for the message bus

a proxy object


Message bus of the DBus service.
a message bus
an instance of the MessageBus class


Full name of a DBus service.


dasbus.loop module

Bases: object

The abstract representation of the event loop.

It is necessary to run the event loop to handle emitted DBus signals or incoming DBus calls (in the DBus service).

Example:

# Create the event loop.
loop = EventLoop()
# Start the event loop.
loop.run()
# Run loop.quit() to stop.


Stop the event loop.

Start the event loop.


Bases: dasbus.loop.AbstractEventLoop

The representation of the event loop.

Stop the event loop.

Start the event loop.


dasbus.namespace module

Create a DBus name from the given names.
namespace -- a sequence of names
a DBus name


Create a DBus path from the given names.
namespace -- a sequence of names
a DBus path


Return a namespace of the DBus name.
name -- a DBus name
a sequence of names


dasbus.signal module

Bases: object

Default representation of a signal.

Connect to a signal.
callback -- a function to register


Disconnect from a signal.

If no callback is specified, then all functions will be unregistered from the signal.

If the specified callback isn't registered, do nothing.

callback -- a function to unregister or None


Emit a signal with the given arguments.


dasbus.specification module

Bases: object

DBus XML specification.






Bases: tuple
Alias for field number 2

Alias for field number 1

Alias for field number 0

Alias for field number 3


Bases: tuple
Alias for field number 1

Alias for field number 0

Alias for field number 2

Alias for field number 4

Alias for field number 3




Bases: tuple
Alias for field number 1

Alias for field number 0

Alias for field number 2


Add a member of a DBus interface.

Return a DBus specification for the given XML.

Get a member of a DBus interface.

Interfaces of the DBus specification.

Members of the DBus specification.


Bases: Exception

Exception for the DBus specification errors.


Bases: object

Class for parsing DBus XML specification.

Generate a representation of a DBus XML specification.
  • xml -- the XML specification to parse
  • factory -- the DBus specification factory

a representation od the DBus specification


alias of dasbus.xml.XMLParser


dasbus.structure module

Bases: object

Object representation of data in a DBus structure.

Classes derived from this class should represent specific types of DBus structures. They will support a conversion from a DBus structure of this type to a Python object and back.

Convert a DBus structure to a data object.
structure -- a DBus structure
a data object


Convert DBus structures to data objects.
structures -- a list of DBus structures
a list of data objects


Convert this data object to a DBus structure.
a DBus structure


Convert data objects to DBus structures.
objects -- a list of data objects
a list of DBus structures



Bases: Exception

General exception for DBus structure errors.


Compare data of the given data objects.
  • obj -- a data object
  • other -- another data object

True if the data is equal, otherwise False


Generate a string representation of a data object.

Set the argument 'skip' to skip attributes with sensitive data.

Set the argument 'add' to add other values to the string representation. The attributes in the string representation will be sorted alphabetically.

  • obj -- a data object
  • skip -- a list of names that should be skipped or None
  • add -- a dictionary of attributes to add or None

a string representation of the data object


dasbus.typing module

alias of bool


alias of float

alias of int





alias of str





Bases: gi.repository.GLib.Variant

new_array(child_type:GLib.VariantType=None, children:list=None) -> GLib.Variant
new_boolean(value:bool) -> GLib.Variant
new_byte(value:int) -> GLib.Variant
new_bytestring(string:list) -> GLib.Variant
new_bytestring_array(strv:list) -> GLib.Variant
new_dict_entry(key:GLib.Variant, value:GLib.Variant) -> GLib.Variant
new_double(value:float) -> GLib.Variant
new_fixed_array(element_type:GLib.VariantType, elements=None, n_elements:int, element_size:int) -> GLib.Variant
new_from_bytes(type:GLib.VariantType, bytes:GLib.Bytes, trusted:bool) -> GLib.Variant
new_from_data(type:GLib.VariantType, data:list, trusted:bool, notify:GLib.DestroyNotify, user_data=None) -> GLib.Variant
new_handle(value:int) -> GLib.Variant
new_int16(value:int) -> GLib.Variant
new_int32(value:int) -> GLib.Variant
new_int64(value:int) -> GLib.Variant
new_maybe(child_type:GLib.VariantType=None, child:GLib.Variant=None) -> GLib.Variant
new_object_path(object_path:str) -> GLib.Variant
new_objv(strv:list) -> GLib.Variant
new_signature(signature:str) -> GLib.Variant
new_string(string:str) -> GLib.Variant
new_strv(strv:list) -> GLib.Variant
new_tuple(children:list) -> GLib.Variant
new_uint16(value:int) -> GLib.Variant
new_uint32(value:int) -> GLib.Variant
new_uint64(value:int) -> GLib.Variant
new_variant(value:GLib.Variant) -> GLib.Variant





Return a list of the element signatures of the topmost signature tuple.

If the signature is not a tuple, it returns one element with the entire signature. If the signature is an empty tuple, the result is [].

This is useful for e. g. iterating over method parameters which are passed as a single Variant.


Decompose a GVariant into a native Python object.


Bases: gi.Boxed

new(type_string:str) -> GLib.VariantType
new_array(element:GLib.VariantType) -> GLib.VariantType
new_dict_entry(key:GLib.VariantType, value:GLib.VariantType) -> GLib.VariantType
new_maybe(element:GLib.VariantType) -> GLib.VariantType
new_tuple(items:list) -> GLib.VariantType

































Bases: dasbus.typing.VariantUnpacking

Class for unpacking variants.

Unpack the specified variant.
variant -- a variant to unpack
an unpacked value



Bases: object

Set of functions of unpacking a variant.

This class is doing the same as the unpack method of the Variant class, but it allows to reuse the code for other variant modifications.


Bases: dasbus.typing.VariantUnpacking

Class for unwrapping variants.

Unwrap the specified variant.
variant -- a variant to unwrap
a unwrapped value



Return DBus representation of a type hint.
type_hint -- a type hint
a string with DBus representation


Decompose a DBus value into a native Python object.

This function is useful for testing, when the DBus library doesn't decompose arguments and return values of DBus calls.

value -- a DBus value
a native Python object


Get the arguments of the type hint.

For example, Str and Int are arguments of the type hint Tuple(Str, Int).

type_hint -- a type hint
a type arguments


Return a variant data type.

The type of a variant is specified with a type hint.

Example:

v1 = get_variant(Bool, True)
v2 = get_variant(List[Int], [1,2,3])


  • type_hint -- a type hint or a type string
  • value -- a value of the variant

an instance of Variant


Return a type of a variant data type.
type_hint -- a type hint or a type string
an instance of VariantType


Is the given base type a base of the specified type hint?

For example, List is a base of the type hint List[Int] and Int is a base of the type hint Int. A class is a base of itself and of every subclass of this class.

  • type_hint -- a type hint
  • base_type -- a base type

True or False


Is the type hint a tuple of one item?
type_hint -- a type hint or a type string
True or False


Unwrap a variant data type.

Unlike the unpack method of the Variant class, this function doesn't recursively unpacks all variants in the data structure. It will unpack only the topmost variant.

The implementation is inspired by the unpack method.

variant -- a variant
a value


dasbus.xml module

Bases: dasbus.xml.XMLParser

Class for generating XML.

Append the child element to the parent element.


Create an interface element.

Create a method element.

Create a node element called node.

Create a parameter element.

Create a property element.

Create a signal element.

Return XML of the element.

Return pretty printed normalized XML.

Python 3.8 changed the order of the attributes and introduced the function canonicalize that should be used to normalize XML.



Bases: object

Class for parsing XML.



Return a dictionary of interfaces defined in a node element.












Examples

Look at the complete examples or DBus services of the Anaconda Installer for more inspiration.

Basic usage

Show the current hostname.

from dasbus.connection import SystemMessageBus
bus = SystemMessageBus()
proxy = bus.get_proxy(


    "org.freedesktop.hostname1",


    "/org/freedesktop/hostname1"
)
print(proxy.Hostname)


Send a notification to the notification server.

from dasbus.connection import SessionMessageBus
bus = SessionMessageBus()
proxy = bus.get_proxy(


    "org.freedesktop.Notifications",


    "/org/freedesktop/Notifications"
)
id = proxy.Notify(


    "", 0, "face-smile", "Hello World!",


    "This notification can be ignored.",


    [], {}, 0
)
print("The notification {} was sent.".format(id))


Handle a closed notification.

from dasbus.loop import EventLoop
loop = EventLoop()
from dasbus.connection import SessionMessageBus
bus = SessionMessageBus()
proxy = bus.get_proxy(


    "org.freedesktop.Notifications",


    "/org/freedesktop/Notifications"
)
def callback(id, reason):


    print("The notification {} was closed.".format(id))
proxy.NotificationClosed.connect(callback)
loop.run()


Asynchronously fetch a list of network devices.

from dasbus.loop import EventLoop
loop = EventLoop()
from dasbus.connection import SystemMessageBus
bus = SystemMessageBus()
proxy = bus.get_proxy(


    "org.freedesktop.NetworkManager",


    "/org/freedesktop/NetworkManager"
)
def callback(call):


    print(call())
proxy.GetDevices(callback=callback)
loop.run()


Define the org.example.HelloWorld service.

class HelloWorld(object):


    __dbus_xml__ = """


    <node>


        <interface name="org.example.HelloWorld">


            <method name="Hello">


                <arg direction="in" name="name" type="s" />


                <arg direction="out" name="return" type="s" />


            </method>


        </interface>


    </node>


    """


    def Hello(self, name):


        return "Hello {}!".format(name)


Define the org.example.HelloWorld service with an automatically generated XML specification.

from dasbus.server.interface import dbus_interface
from dasbus.typing import Str
@dbus_interface("org.example.HelloWorld")
class HelloWorld(object):


    def Hello(self, name: Str) -> Str:


        return "Hello {}!".format(name)
print(HelloWorld.__dbus_xml__)


Publish the org.example.HelloWorld service on the session message bus.

from dasbus.connection import SessionMessageBus
bus = SessionMessageBus()
bus.publish_object("/org/example/HelloWorld", HelloWorld())
bus.register_service("org.example.HelloWorld")
from dasbus.loop import EventLoop
loop = EventLoop()
loop.run()


Support for Unix file descriptors

The support for Unix file descriptors is disabled by default. It needs to be explicitly enabled when you create a DBus proxy or publish a DBus object that could send or receive Unix file descriptors.

WARNING:

This functionality is supported only on UNIX.


Send and receive Unix file descriptors with a DBus proxy.

import os
from dasbus.connection import SystemMessageBus
from dasbus.unix import GLibClientUnix
bus = SystemMessageBus()
proxy = bus.get_proxy(


    "org.freedesktop.login1",


    "/org/freedesktop/login1",


    client=GLibClientUnix
)
fd = proxy.Inhibit(


    "sleep", "my-example", "Running an example", "block"
)
proxy.ListInhibitors()
os.close(fd)


Allow to send and receive Unix file descriptors within the /org/example/HelloWorld DBus object.

from dasbus.unix import GLibServerUnix
bus.publish_object(


    "/org/example/HelloWorld",


    HelloWorld(),


    server=GLibServerUnix
)


Management of DBus names and paths

Use constants to define DBus services and objects.

from dasbus.connection import SystemMessageBus
from dasbus.identifier import DBusServiceIdentifier, DBusObjectIdentifier
NETWORK_MANAGER_NAMESPACE = (


    "org", "freedesktop", "NetworkManager"
)
NETWORK_MANAGER = DBusServiceIdentifier(


    namespace=NETWORK_MANAGER_NAMESPACE,


    message_bus=SystemMessageBus()
)
NETWORK_MANAGER_SETTINGS = DBusObjectIdentifier(


    namespace=NETWORK_MANAGER_NAMESPACE,


    basename="Settings"
)


Create a proxy of the org.freedesktop.NetworkManager service.

proxy = NETWORK_MANAGER.get_proxy()
print(proxy.NetworkingEnabled)


Create a proxy of the /org/freedesktop/NetworkManager/Settings object.

proxy = NETWORK_MANAGER.get_proxy(NETWORK_MANAGER_SETTINGS)
print(proxy.Hostname)


See a complete example.

Error handling

Use exceptions to propagate and handle DBus errors. Create an error mapper and a decorator for mapping Python exception classes to DBus error names.

from dasbus.error import ErrorMapper, DBusError, get_error_decorator
error_mapper = ErrorMapper()
dbus_error = get_error_decorator(error_mapper)


Use the decorator to register Python exceptions that represent DBus errors. These exceptions can be raised by DBus services and caught by DBus clients in the try-except block.

@dbus_error("org.freedesktop.DBus.Error.InvalidArgs")
class InvalidArgs(DBusError):


    pass


The message bus will use the specified error mapper to automatically transform Python exceptions to DBus errors and back.

from dasbus.connection import SessionMessageBus
bus = SessionMessageBus(error_mapper=error_mapper)


See a complete example.

Timeout for a DBus call

Call DBus methods with a timeout (specified in milliseconds).

proxy = NETWORK_MANAGER.get_proxy()
try:


    proxy.CheckConnectivity(timeout=3)
except TimeoutError:


    print("The call timed out!")


Support for DBus structures

Represent DBus structures by Python objects. A DBus structure is a dictionary of attributes that maps attribute names to variants with attribute values. Use Python objects to define such structures. They can be easily converted to a dictionary, send via DBus and converted back to an object.

from dasbus.structure import DBusData
from dasbus.typing import Str, get_variant
class UserData(DBusData):


    def __init__(self):


        self._name = ""


    @property


    def name(self) -> Str:


        return self._name


    @name.setter


    def name(self, name):


        self._name = name
data = UserData()
data.name = "Alice"
print(UserData.to_structure(data))
print(UserData.from_structure({


    "name": get_variant(Str, "Bob")
}))


See a complete example.

Management of dynamic DBus objects

Create Python objects that can be automatically published on DBus. These objects are usually managed by DBus containers and published on demand.

from dasbus.server.interface import dbus_interface
from dasbus.server.template import InterfaceTemplate
from dasbus.server.publishable import Publishable
from dasbus.typing import Str
@dbus_interface("org.example.Chat")
class ChatInterface(InterfaceTemplate):


    def Send(self, message: Str):


        return self.implementation.send()
class Chat(Publishable):


    def for_publication(self):


        return ChatInterface(self)


    def send(self, message):


        print(message)


Use DBus containers to automatically publish dynamically created Python objects. A DBus container converts publishable Python objects into DBus paths and back. It generates unique DBus paths in the specified namespace and assigns them to objects. Each object is published when its DBus path is requested for the first time.

from dasbus.connection import SessionMessageBus
from dasbus.server.container import DBusContainer
container = DBusContainer(


    namespace=("org", "example", "Chat"),


    message_bus=SessionMessageBus()
)
print(container.to_object_path(Chat()))


See a complete example.

INDICES AND TABLES

  • genindex
  • modindex
  • search

AUTHOR

Vendula Poncova

COPYRIGHT

2022, Vendula Poncova

December 15, 2022