cbor2 3.0.0

Pure Python CBOR (de)serializer with extensive tag support

This library provides encoding and decoding for the Concise Binary Object Representation (CBOR) (RFC 7049) serialization format.

Usage

from cbor2 import *

# Serialize an object as a bytestring
data = dumps(['hello', 'world'])

# Deserialize a bytestring
obj = loads(data)

# Efficiently deserialize from a file
with open('input.cbor', 'rb') as fp:
    obj = load(fp)

# Efficiently serialize an object to a file
with open('output.cbor', 'wb') as fp:
    dump(obj, fp)

String/bytes handling on Python 2

The str type is encoded as binary on Python 2. If you want to encode strings as text on Python 2, use unicode strings instead.

Date/time handling

CBOR does not support naïve datetimes (that is, datetimes where tzinfo is missing). When the encoder encounters such a datetime, it needs to know which timezone it belongs to. To this end, you can specify a default timezone by passing a datetime.tzinfo instance to dump()/dumps() call as the timezone argument. Decoded datetimes are always timezone aware.

By default, datetimes are serialized in a manner that retains their timezone offsets. You can optimize the data stream size by passing datetime_as_timestamp=False to dump()/dumps(), but this causes the timezone offset information to be lost.

Cyclic (recursive) data structures

By default, both the encoder and decoder support cyclic data structures (ie. containers that contain references to themselves). When serializing, this requires some extra space in the data stream. If you know you won’t have cyclic structures in your data, you can save a little bit of space by turning off the value sharing feature by passing the value_sharing=False option to dump()/dumps().

Customizing encoding/decoding

The encoder allows you to specify a mapping of types to callables that handle the encoding of some otherwise unsupported type. The decoder, on the other hand, allows you to specify a mapping of semantic tag numbers to callables that implement custom transformation logic for tagged values.

Custom encoder and decoder hooks can also be made to support value sharing. For encoder hooks, wrapping them with @cbor2.shareable_encoder is enough. Decoder hooks are slightly more complex. In order to support cyclic references, the decoder must construct a “raw” instance of the target class (usually using __new__()) and then separately decoding and applying the object’s state.

See the docstrings of cbor2.CBOREncoder, cbor2.CBORDecoder and @cbor2.shareable_encoder for details.

Tag support

In addition to all standard CBOR tags, this library supports many extended tags:

Tag	Semantics	Python type(s)
0	Standard date/time string	datetime.date / datetime.datetime
1	Epoch-based date/time	datetime.date / datetime.datetime
2	Positive bignum	int / long
3	Negative bignum	int / long
4	Decimal fraction	decimal.Decimal
5	Bigfloat	decimal.Decimal
28	Mark shared value	N/A
29	Reference shared value	N/A
30	Rational number	fractions.Fraction
35	Regular expression	_sre.SRE_Pattern (result of re.compile(...))
36	MIME message	email.message.Message
37	Binary UUID	uuid.UUID

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