Python Protocol Buffers differences

protobuf_test.py

#!/usr/bin/env python3
# Test file demonstrating issues from
# https://github.com/protocolbuffers/protobuf/pull/5166
# Try running with PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python
# and with PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp

import subprocess

proto_definition = """
syntax = "proto2";

message TestMessage
{
  optional int32 value = 1;
}
"""

with open('test.proto', 'w') as f:
    f.write(proto_definition)
subprocess.check_call(['protoc', '--python_out=.', 'test.proto'])

import test_pb2  # noqa

test_message = test_pb2.TestMessage()
print(test_message.ParseFromString(b'test'))