QMP Messages

QMP Message Format

This module provides the Message class, which represents a single QMP message sent to or from the server.

class qemu.qmp.message.Message(value: bytes | Mapping[str, object] = b'{}', *, eager: bool = True)

Bases: MutableMapping[str, object]

Represents a single QMP protocol message.

QMP uses JSON objects as its basic communicative unit; so this Python object is a MutableMapping. It may be instantiated from either another mapping (like a dict), or from raw bytes that still need to be deserialized.

Once instantiated, it may be treated like any other MutableMapping:

>>> msg = Message(b'{"hello": "world"}')
>>> assert msg['hello'] == 'world'
>>> msg['id'] = 'foobar'
>>> print(msg)
{
  "hello": "world",
  "id": "foobar"
}

It can be converted to bytes:

>>> msg = Message({"hello": "world"})
>>> print(bytes(msg))
b'{"hello":"world","id":"foobar"}'

Or back into a garden-variety dict:

>>> dict(msg)
{'hello': 'world'}

Or pretty-printed:

>>> print(str(msg))
{
  "hello": "world"
}

Parameters:

• value – Initial value, if any.

• eager – When True, attempt to serialize or deserialize the initial value immediately, so that conversion exceptions are raised during the call to __init__().

exception qemu.qmp.message.DeserializationError(error_message: str, raw: bytes)

Bases: ProtocolError

A QMP message was not understood as JSON.

When this Exception is raised, __cause__ will be set to the json.JSONDecodeError Exception, which can be interrogated for further details.

Parameters:

• error_message – Human-readable string describing the error.

• raw – The raw bytes that prompted the failure.

raw: bytes

The raw bytes that were not understood as JSON.

exception qemu.qmp.message.UnexpectedTypeError(error_message: str, value: object)

Bases: ProtocolError

A QMP message was JSON, but not a JSON object.

Parameters:

• error_message – Human-readable string describing the error.

• value – The deserialized JSON value that wasn’t an object.

value: object

The JSON value that was expected to be an object.

QMP Data Models

QMP Data Models

This module provides simplistic data classes that represent the few structures that the QMP spec mandates; they are used to verify incoming data to make sure it conforms to spec.

class qemu.qmp.models.Model(raw: Mapping[str, Any])

Bases: object

Abstract data model, representing some QMP object of some kind.

Parameters:

raw – The raw object to be validated.

Raises:

• KeyError – If any required fields are absent.

• TypeError – If any required fields have the wrong type.

class qemu.qmp.models.Greeting(raw: Mapping[str, Any])

Bases: Model

Defined in qmp-spec.txt, section 2.2, “Server Greeting”.

See 2.2 Server Greeting for details.

Parameters:

raw – The raw Greeting object.

Raises:

• KeyError – If any required fields are absent.

• TypeError – If any required fields have the wrong type.

QMP: QMPGreeting

‘QMP’ member

class qemu.qmp.models.QMPGreeting(raw: Mapping[str, Any])

Bases: Model

Defined in qmp-spec.txt, section 2.2, “Server Greeting”.

Parameters:

raw – The raw QMPGreeting object.

Raises:

• KeyError – If any required fields are absent.

• TypeError – If any required fields have the wrong type.

version: Mapping[str, object]

‘version’ member

capabilities: Sequence[object]

‘capabilities’ member

class qemu.qmp.models.ErrorResponse(raw: Mapping[str, Any])

Bases: Model

Defined in qmp-spec.txt, section 2.4.2, “error”.

Parameters:

raw – The raw ErrorResponse object.

Raises:

• KeyError – If any required fields are absent.

• TypeError – If any required fields have the wrong type.

error: ErrorInfo

‘error’ member

id: object | None

‘id’ member

class qemu.qmp.models.ErrorInfo(raw: Mapping[str, Any])

Bases: Model

Defined in qmp-spec.txt, section 2.4.2, “error”.

Parameters:

raw – The raw ErrorInfo object.

Raises:

• KeyError – If any required fields are absent.

• TypeError – If any required fields have the wrong type.

class_: str

‘class’ member, with an underscore to avoid conflicts in Python.

desc: str

‘desc’ member