msgpack – Pack object in msgpack format

The msgpack format is similar to json, except that the encoded data is binary. See https://msgpack.org for details. The module implements a subset of the cpython module msgpack-python.

Not implemented: 64-bit int, uint, float.

For more information about working with msgpack, see the CPython Library Documentation.

Example 1:

import msgpack
from io import BytesIO

b = BytesIO()
msgpack.pack({'list': [True, False, None, 1, 3.14], 'str': 'blah'}, b)
b.seek(0)
print(msgpack.unpack(b))

Example 2: handling objects:

from msgpack import pack, unpack, ExtType
from io import BytesIO

class MyClass:
    def __init__(self, val):
        self.value = val
    def __str__(self):
        return str(self.value)

data = MyClass(b'my_value')

def encoder(obj):
    if isinstance(obj, MyClass):
        return ExtType(1, obj.value)
    return f"no encoder for {obj}"

def decoder(code, data):
    if code == 1:
        return MyClass(data)
    return f"no decoder for type {code}"

buffer = BytesIO()
pack(data, buffer, default=encoder)
buffer.seek(0)
decoded = unpack(buffer, ext_hook=decoder)
print(f"{data} -> {buffer.getvalue()} -> {decoded}")

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msgpack.pack(obj: object, stream: circuitpython_typing.ByteStream, *, default: Union[Callable[[object], None], None] = None) None

Output object to stream in msgpack format.

Parameters
  • obj (object) – Object to convert to msgpack format.

  • stream (ByteStream) – stream to write to

  • default (Optional[Callable[[object], None]]) – function called for python objects that do not have a representation in msgpack format.

msgpack.unpack(stream: circuitpython_typing.ByteStream, *, ext_hook: Union[Callable[[int, bytes], object], None] = None, use_list: bool = True) object

Unpack and return one object from stream.

Parameters
  • stream (ByteStream) – stream to read from

  • ext_hook (Optional[Callable[[int, bytes], object]]) – function called for objects in msgpack ext format.

  • use_list (Optional[bool]) – return array as list or tuple (use_list=False).

Return object

object read from stream.

class msgpack.ExtType(code: int, data: bytes)

ExtType represents ext type in msgpack.

Constructor :param int code: type code in range 0~127. :param bytes data: representation.

code :int

The type code, in range 0~127.

data :bytes

Data.