Looping over Protocol Buffers attributes in Python

Question

I would like help with recursively looping over all attributes/sub objects contained in a protocol buffers message, assuming that we do not know the names of them, or how many t

Answer 1

I'm not super familiar with protobufs, so there may well be an easier way or api for this kind of thing. However, below shows an example of how you could iterate/introspect and objects fields and print them out. Hopefully enough to get you going in the right direction at least...

import addressbook_pb2 as addressbook

person = addressbook.Person(id=1234, name="John Doe", email="foo@example.com")
person.phone.add(number="1234567890")


def dump_object(obj):
    for descriptor in obj.DESCRIPTOR.fields:
        value = getattr(obj, descriptor.name)
        if descriptor.type == descriptor.TYPE_MESSAGE:
            if descriptor.label == descriptor.LABEL_REPEATED:
                map(dump_object, value)
            else:
                dump_object(value)
        elif descriptor.type == descriptor.TYPE_ENUM:
            enum_name = descriptor.enum_type.values[value].name
            print "%s: %s" % (descriptor.full_name, enum_name)
        else:
            print "%s: %s" % (descriptor.full_name, value)

dump_object(person)

which outputs

tutorial.Person.name: John Doe
tutorial.Person.id: 1234
tutorial.Person.email: foo@example.com
tutorial.Person.PhoneNumber.number: 1234567890
tutorial.Person.PhoneNumber.type: HOME