Hello,
I am trying to build self-describing messages using Python. I read through
the
documentation
https://protobuf.dev/programming-guides/techniques/#self-description
as well as through the Python
API https://googleapis.dev/python/protobuf/latest/google/protobuf.html, but
I am still not very sure about how to do that.
I started with the example message
syntax = "proto3"; import "google/protobuf/any.proto"; import
"google/protobuf/descriptor.proto"; message SelfDescribingMessage { // Set
of FileDescriptorProtos which describe the type and its dependencies.
google.protobuf.FileDescriptorSet descriptor_set = 1; // The message and
its type, encoded as an Any message. google.protobuf.Any message = 2; }
And I would like to pass through it a simple addressbook message
syntax = "proto2";
package tutorial;
message AddressBook {
optional string name = 1;
optional string number = 2;
}
The AddressBook message would be contained in the message field and the
descriptor_set field would contain the descriptor of the proto above.
However I could not do this no matter what I have tried.
The closest I got was exporting a file descriptor set from the
SelfDescribingMessage.proto given in the documentation as "protoc
--proto_path=. --proto_path=./include
--descriptor_set_out=./self_describing_ds --include_imports
self_describing.proto" and then reading it
with open("self_describing_ds", 'rb') as fh:
fds = descriptor_pb2.FileDescriptorSet.FromString(fh.read())
message_classes = message_factory.GetMessages(fds.file)
my_proto_instance = message_classes["SelfDescribingMessage"]()
address_book = addressbook_pb2.AddressBook()
address_book.name = "John Doe"
address_book.number = "123456"
my_proto_instance.message.Pack(address_book)
I am not able to set my_proto_instance.descriptor_set though. Extracting
address book descriptor set using protoc and then reading it and trying to
append it
with open("addressbook_ds", 'rb') as fh:
addressbook_fds =
descriptor_pb2.FileDescriptorSet.FromString(fh.read())
my_proto_instance.descriptor_set.file.append(addressbook_fds)
fails on
TypeError: Parameter to MergeFrom() must be instance of same class:
expected <class 'FileDescriptorProto'> got <class
'google.protobuf.descriptor_pb2.FileDescriptorProto'>.
I could not get any closer.
Does anyone have any simple example on sending the self-describing messages
in Python, please?
Thanks a lot in advance.
Jan
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