Protobuf Schema Parser is a pure-Python library that parses and writes Protobuf schemas to and from an abstract syntax tree (AST).

The library uses proto_schema_parser.parser.Parser to parse the CST into an AST. The proto_schema_parser.generator.Generator class converts the AST back into a CST (a Protobuf schema string).

The lexer and parser are autogenerated from Buf's ANTLR lexer and parser grammar files.

• ✅ proto2 and proto3 support
• ✅ protobuf editions support (edition 2023, edition 2024)
• ✅ message, field, enum, optional, required, repeated
• ✅ import, package, oneof, map, and option
• ✅ group and extend (in proto2)
• ✅ service, rpc, and stream
• ✅ line and block comment preservation

Install the package via pip:

pip install proto-schema-parser

To parse a protobuf schema, create a Parser object and call the parse method:

from proto_schema_parser.parser import Parser

text = """
syntax = "proto3";

message SearchRequest {
  string query = 1;
  int32 page_number = 2;
  int32 result_per_page = 3;
}
"""

result = Parser().parse(text)

This will return an AST object (ast.File) representing the parsed protobuf schema.

File(
  syntax='proto3',
  file_elements=[
    Message(
      name='SearchRequest',
      elements=[
        Field(
          name='query',
          number=1,
          type='string',
          cardinality=None,
          options=[]),
        Field(
          name='page_number',
          number=2,
          type='int32',
          cardinality=None,
          options=[]),
        Field(
          name='result_per_page',
          number=3,
          type='int32',
          cardinality=None,
          options=[])])])

To write the AST back to a protobuf schema, create a Generator object and call the generate method:

from proto_schema_parser.generator import Generator

proto = Generator().generate(result)

The proto variable now contains the string:

syntax = "proto3";
message SearchRequest {
  string query = 1;
  int32 page_number = 2;
  int32 result_per_page = 3;
}

The library also supports protobuf editions, which provide more flexibility than proto2/proto3 syntax:

from proto_schema_parser.parser import Parser
from proto_schema_parser.generator import Generator

# Parse a protobuf file using edition syntax
text = """
edition = "2023";

message SearchRequest {
  string query = 1;
  int32 page_number = 2;
}
"""

result = Parser().parse(text)
# result.edition will be "2023"
# result.syntax will be None

# Generate back to protobuf format
proto = Generator().generate(result)

Supported editions:

• edition = "2023"; - Edition 2023 spec
• edition = "2024"; - Edition 2024 spec

I welcome contributions!

• Submit a PR and I'll review it as soon as I can.
• Open an issue if you find a bug or have a feature request.

Protobuf Schema Parser is licensed under the MIT license.