When constructing an instance of a Python protobuf message, I keep getting positional argument error

Question

I'm using pb_2 and want to consturct instances of a message but keep facing positional argument error. I can construct instances from all other messages but when it comes to the following example, I get stcuk.

I have the following three messages:

message Foo {
   int32 num = 1;
   repeated KeyValuePair features = 2;  
}

message KeyValuePair {
   string key = 1;
   Value value = 2;
}

message Value {
   oneof oneOfValue {
      string strValue = 1;
      int64 intValue = 2;
   }
}

I want to construct an instance of Foo that looks like this:

foo {
      num: 123
      features: [KeyValuePair {key: 'key1', value: 'value1'},
                 KeyValuePair {key: 'key2', value: 'value2'}]
    }

I tried the following and keep getting positional argument error ('no positional arguments allowed'):

my_foo = Foo(num=123, 
             features=[KeyValuePair(key='key1', value='value1'),
                       KeyValuePair(key='key2', value='value2')])

I am not using any positional arguments. Can anyone help?

Thanks!

larsks · Accepted Answer · 2023-07-10 13:53:27Z

1

With the caveat that I am not familiar with protobuf...aren't you instantiating Foo incorrectly? You've declared that a KeyValuePair looks like:

message KeyValuePair {
   string key = 1;
   Value value = 2;
}

So it maps a string value to a Value instance. That means you would need:

my_foo = Foo(
    num=123,
    features=[
        KeyValuePair(key="key1", value=Value(strValue="value1")),
        KeyValuePair(key="key2", value=Value(strValue="value2")),
    ],
)

On my system, using your example .proto file (adding syntax = "proto3"; at the top), that runs without errors.

answered Jul 10, 2023 at 13:53

larsks

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1 Comment

mahb Over a year ago

You are right! What a mistake. Thanks for catching it. It runs now. Cheers!

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