Python DSL to leverage translation of dictionaries and SQLAlchemy into Protobuf objects.

Primarily created with the intention of migrating python services to support gRPC.

What is Mercator ?

Mercator is a Python library that simplifies the following of serializing dictionary data into Protobuf binary data.

Mercator actually supports extracting data from:

  • dictionaries
  • SQLAlchemy model instances
  • Any opaque python objects (e.g.: namedtuple())

When should I use Mercator ?

  • When migrating custom implementations of RPC to gGRPC.
  • When migrating in-memory data to Protobuf.

When should I not use Mercator ?

  • When writing gRPC services from scratch.
  • When writing anything that uses Protobuf gets called.

A Data Mapper for Protobuf

This library is primarily intended to aid the migration of python-based microservices to gRPC by leveraging a DSL that resembles ORM and ActiveRecord patterns.

It supports mapping key/values from dictionaries to Protobuf 3 as well as SQLAlchemy ORM models intro Protobuf 3.

Example Usage

from myproject.mappings import (

from . import avengers_pb2

class AvengersService(avengers_pb2.HeroServicer):
    def GetHulk(self):
        info = {
            'login': 'Hulk',
            'email': '',
            'tokens': [
                    'data': 'this is the token',
                    'created_at': 1552240433,
                    'expires_at': 1552240733,
        return UserMapping(info).to_protobuf()