A declarative implementation of BARE that supports streaming

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A declarative implementation of the BARE message format for Python 3.10+

pybare is a general purpose library for strongly typed primitives in Python that supports serializing to and from BARE messages.

pip install pybare


  • Provide a declarative structure for defining types
  • Validation on value updates
  • Support streaming messages


pybare fully implements all BARE types for both encoding and decoding. This includes reading multiple messages from the same BinaryIO stream.

It is well tested and in use on production systems.


We use "Array" / "array" instead of "List" / "list" to avoid conflicts with Python's common builtin type of the same name.


An example that defines the types used as an example in the RFC may be found in example.py

pybare currently requires you define your structures by hand. Examples can be found in the tests.


The general convention is type identifiers start with a capital letter and anonymous generating functions begin with a lowercase. This follows general "pythonic" style for classes vs functions.

from bare import Struct, map, Str, UInt, optional, data, array, Void, struct, U8

# Alternatively, class Data(size=64): ...
PubKey = data(64) # 512 bits

class User(Struct):
    username = Field(Str)
    userid = Field(Int)
    email = Field(optional(Str))
    keys = Field(map(Str, PubKey))
    repos = Field(array(Str)) # variable length array
    # anonymous array and struct
    friends = Field(array(struct(name=Str, age=U8)))

noah = User(username="chiefnoah", userid=1, email=Void(), keys={}, repos=[], friends=[])
noah.username == 'chiefnoah'
noah.username = 'someoneelse'
noah.username == 'someoneelse'
noah.userid == 1 # True
noah.username = 1 # raise: bare.ValidationError
noah.keys # {} (empty dict)
noah.keys['my key'] = bytes(64) #\x00\x00...
noah.keys['oops'] = bytes(1) # raise: bare.ValidationError
noah.email == Void() # True
noah.email = 12345 # raise: bare.ValidationError
noah.pack() # \x00\x01 ... (binary data)

Note, you must wrap the desired type in a Field to get its 'magic' behavior. Class or instance fields that are not wrapped in a Field will be ignored by the pack and unpack methods.

To contribute, send patches to ~chiefnoah/inbox@lists.sr.ht