How to send custom header (metadata) with Python gRPC?

Question

I want to know how to send custom header (or metadata) using Python gRPC. I looked into documents and I couldn't find anything.

Answer 1

I figured out reading the code. You can send a metadata param to the function call, where metadata is a tuple of 2-tuples:

metadata = (('md-key', 'some value'),
            ('some-md-key', 'another value'))
response = stub.YourFunctionCall(request=request, metadata=metadata)

Answer 2

Pls read the example in github. For example:

        response, call = stub.SayHello.with_call(
            helloworld_pb2.HelloRequest(name='you'),
            metadata=(
                ('initial-metadata-1', 'The value should be str'),
                ('binary-metadata-bin',
                 b'With -bin surffix, the value can be bytes'),
                ('accesstoken', 'gRPC Python is great'),
            ))

Or if you want to define a interceptor

        metadata = []
        if client_call_details.metadata is not None:
            metadata = list(client_call_details.metadata)
        metadata.append((
            header,
            value,
        ))
        client_call_details = _ClientCallDetails(
            client_call_details.method, client_call_details.timeout, metadata,
            client_call_details.credentials)

Something important is that the metadata's key can not has upper case character (It has troubled me for a long time).