MessagePack Python Binding

author

INADA Naoki

version

0.2.0

date

2012-06-27

HOW TO USE

one-shot pack & unpack

Use packb for packing and unpackb for unpacking. msgpack provides dumps and loads as alias for compatibility with json and pickle.

pack and dump packs to file-like object. unpack and load unpacks from file-like object.

>>> import msgpack >>> msgpack.packb([1, 2, 3]) 'x93x01x02x03' >>> msgpack.unpackb(_) (1, 2, 3)

unpack unpacks msgpack's array to Python's tuple. To unpack it to list, Use use_list option.

>>> msgpack.unpackb(b'x93x01x02x03', use_list=True) [1, 2, 3]

Read docstring for other options.

streaming unpacking

Unpacker is "streaming unpacker". It unpacks multiple objects from one stream.

import msgpack
from io import BytesIO

buf = BytesIO()
for i in range(100):
   buf.write(msgpack.packb(range(i)))

buf.seek(0)

unpacker = msgpack.Unpacker()
while True:
    data = buf.read(16)
    if not data:
        break
    unpacker.feed(data)

    for unpacked in unpacker:
        print unpacked

packing/unpacking of custom data type

Also possible to pack/unpack user's data types. Here is an example for datetime.datetime.

import datetime

import msgpack

useful_dict = {
    "id": 1,
    "created": datetime.datetime.now(),
}

def decode_datetime(obj):
    if b'__datetime__' in obj:
        obj = datetime.datetime.strptime(obj["as_str"], "%Y%m%dT%H:%M:%S.%f")
    return obj

def encode_datetime(obj):
    if isinstance(obj, datetime.datetime):
        return {'__datetime__': True, 'as_str': obj.strftime("%Y%m%dT%H:%M:%S.%f")}
    return obj


packed_dict = msgpack.packb(useful_dict, default=encode_datetime)
this_dict_again = msgpack.unpackb(packed_dict, object_hook=decode_datetime)

INSTALL

You can use pip or easy_install to install msgpack:

$ easy_install msgpack-python
  or
$ pip install msgpack-python

Windows

msgpack provides some binary distribution for Windows. You can install msgpack without compiler with them.

When you can't use binary distribution, you need to install Visual Studio or Windows SDK on Windows. (NOTE: Visual C++ Express 2010 doesn't support amd64. Windows SDK is recommanded way to build amd64 msgpack without any fee.)

TEST

MessagePack uses nosetest for testing. Run test with following command:

$ nosetests test