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A light full Python3 Protocol Buffers implementation

Project description

lightprotobuf

Introduction

lightprotobuf is a full Python 3 implementation of the Protocol Buffers as described by Google.

Documentation

The main class to use is lightprotobuf.Message

It must be the base class of every messages you define. The rest follows the .proto design:

This message:

enum FooEnum {
   FIELD = 5;
   FIELD2 = 6;
}

message FooMsg {
   required int32 foo_field = 1;
   optional FooEnum foo_enum = 2;
   enum BarEnum {
      FIELD = 5;
      BAR = 6;
   }
   required BarEnum bar_enum = 3;
}

message BarMsg {
   required FooMsg.BarEnum bar_enum = 1;
}

Is translated in python with:

from enum import IntEnum
from lightprotobuf import *
class FooEnum(IntEnum):
     FIELD = 5
     FIELD2 = 6

class FooMsg(Message):
     class BarEnum(IntEnum):
             FIELD = 5
             BAR = 6
     foo_field = Field(1, Int32, Field.REQUIRED, **{})
     bar_enum = Field(3, BarEnum, Field.REQUIRED, **{})
     foo_enum = Field(2, FooEnum, Field.OPTIONAL, **{})

class BarMsg(Message):
     bar_enum = Field(1, FooMsg.BarEnum, Field.REQUIRED, **{})

As you can see, the fields folows this template

<name> = Field(<tag number>, <type>, Field.<REQUIRED|OPTIONEL|REPEATED>, **{<options as a dict (optional)>}

Enums are python’s enum.IntEnum

Nested type are reals python nested types referenced just like in .proto

Interface

The fields are actually transformed as attribute via descriptors. So you can access fields easily:

m = FooMsg()
m.foo_field = 5
m.foo_field # returns 5
m.foo_enum = 5 # Error because it expects a FooEnum object
m.foo_enum = FooEnum.FIELD # OK
m.bar_enum = FooMsg.BarEnum.BAR # OK

Repeated fields expect iterables.

To encode a message, lightprotobuf uses stream objects : each DataType has a to_stream and from_stream class method. Just to call it from a message to encode/decode a message:

import io
s = io.BytesIO()
Message.to_stream(s, m)
s.getvalue() # b'\x06\x08\x05\x10\x05\x18\x06'

m = FooMsg()
s = io.BytesIO(b'\x06\x08\x05\x10\x05\x18\x06')
m = Message.from_stream(s)

_Note_ : if required field is missing, it raises a FieldNotOptional exception

Project details


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