How deserialize protocol buffers from http response use python - python-3.x

Question

I want to deserialize an API response to a python object whose content-type is protobuf, I use the ParseFromString method to parse the HTTP response, but only get a number 23, print the response content directly is b'\n\x08Hi,py-pb'. So, how do I deserialize the HTTP response to the python object?
proto file content:
syntax = "proto3";
package greet;
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply);
}
// The request message containing the user's name.
message HelloRequest {
string name = 1;
}
// The response message containing the greetings.
message HelloReply {
string message = 1;
}
python code:
# _*_ coding: utf8 _*_
from google.protobuf.json_format import ParseDict, MessageToJson
from protos.greet_pb2 import HelloRequest, HelloReply
import httpx
import asyncio
async def send_req():
req = {'name': 'py-pb'}
msg = ParseDict(req, HelloRequest())
print(msg)
print(type(msg))
print(msg.SerializeToString())
async with httpx.AsyncClient() as client:
resp = await client.post('http://localhost:5044/greet/Greeter/SayHello', data=msg.SerializeToString(),
headers={'Accept': 'application/protobuf', 'Content-Type': 'application/protobuf'})
print('=========response=========')
# print(resp.stream)
# print(resp.content)
# print(resp.text)
resp_msg = HelloReply().ParseFromString(resp.content)
# resp_msg = HelloReply().SerializeToString(resp.content)
print(resp_msg)
asyncio.run(send_req())
Versions:
Python - 3.10.5
google.protobuf - 4.21.2
Related answer:
ParseFromString is a method -- it does not return anything, but rather fills in self with the parsed content.
Reference:
Google Protocol Buffers (protobuf) in Python3 - trouble with ParseFromString (encoding?)

Answer 1

ParseFromString is an instance method. So you want, e.g.:
hello_reply = HelloReply()
hello_reply.ParseFromString(resp.content)
The docs include an example using ParseFromString.
Here's a repro:
from google.protobuf.json_format import ParseDict, MessageToJson
from greet_pb2 import HelloRequest, HelloReply
rqst = {'name': 'py-pb'}
msg = ParseDict(rqst, HelloRequest())
tx = msg.SerializeToString()
print(tx)
print(tx.hex())
resp = HelloReply()
resp.ParseFromString(tx)
print(resp)
Yields:
b'\n\x05py-pb'
0a0570792d7062
message: "py-pb"
You can take the binary as hex and plug it into protogen to decode it.
Field #1: 0A String Length = 5, Hex = 05, UTF8 = "py-pb"