Python grpc: AttributeError 'NoneType' object has no attribute 'unary_unary'

Question

My first time playing around with Python and grpc. I have been troubleshooting for a while now and cant seem to get past the below issue.

I am getting the following error by running: venv/bin/python placeholder.py (excuse the file name Im still sandboxing).

Error:

Traceback (most recent call last):
  File "placeholder.py", line 50, in <module>
    client = BitcClient()
  File "placeholder.py", line 20, in __init__
    self.stub = pb2_grpc.BranchesStub(self.channel)
  File "/Users/me/PycharmProjects/app/infrastructure/v3/branches_pb2_grpc.py", line 18, in __init__
    self.ListBranches = channel.unary_unary(
AttributeError: 'NoneType' object has no attribute 'unary_unary'

Here are the specs of my setup:

Specs:

certifi==2022.6.15
charset-normalizer==2.1.1
grpcio==1.39.0
grpcio-tools==1.39.0
idna==3.3
protobuf==3.20.1
requests==2.28.1
six==1.16.0
urllib3==1.26.12

(venv) % venv/bin/python --version
Python 3.8.9

Here is my client code. The server code I do not have access to as it is built by another team.

Client code:

import grpc
import app.infrastructure.v3.branches_pb2 as pb2
import app.infrastructure.v3.branches_pb2_grpc as pb2_grpc

class Client(object):
    
    def __init__(self):
        self.server = 'api.domain.com:443'
    
        # instantiate a channel
        self.channel = grpc.insecure_channel('{}'.format(self.server))
        self.channel = grpc.channel_ready_future(self.channel).result(timeout=3)
    
        # bind the client and the server
        self.stub = pb2_grpc.BranchesStub(self.channel)
    
    def get_branches(self, message):
        message = pb2.ListBranchesResponse(message=message)
        print(f'{message}')
        return self.stub.ListBranches(message)

if __name__ == '__main__':

    api_client = Client()
    result = api_client()

Below is relevant code that was generated from .proto files:

Proto generated code:

class BranchesStub(object):
    """Operations to manage branches and their releation to projects.
    """

    def __init__(self, channel):
        """Constructor.

        Args:
            channel: A grpc.Channel.
        """
        self.ListBranches = channel.unary_unary(
                '/app.infrastructure.v3.Branches/ListBranches',
            

    request_serializer=dot_app_dot_infrastructure_dot_v3_dot_branches__pb2.ListBranchesRequest.SerializeToString,
                    response_deserializer=dot_app_dot_infrastructure_dot_v3_dot_branches__pb2.ListBranchesResponse.FromString,
                    )
    ...

class BranchesServicer(object):
    """Operations to manage branches and their releation to Console projects.
    """

    def ListBranches(self, request, context):
        """List all created branches (and their status) for the specified project
        """
        context.set_code(grpc.StatusCode.UNIMPLEMENTED)
        context.set_details('Method not implemented!')
        raise NotImplementedError('Method not implemented!')

Help would be greatly appreciated!

Answer 1

Turns out issue was caused by this line:

self.channel = grpc.channel_ready_future(self.channel).result(timeout=3)

This line worked when I used it during another unrelated client.py file. Not sure why its failing now but at least my code seems to work now after removing it.