Adding a primitive type repeated field in a protobuf from python

Question

I have a proto2 file defined like the following:

message X {
  repeated A a = 1;
  repeated B b = 2;
}

message BtoOtherBEntry {
  required uint64 parent_b = 1; // key
  repeated uint64 children_b = 2; // value
}

Then I have a python code that maps a type uint64 B to a list of B. Let's say this is BtoBMap.

I am trying to populate X.b

        X x
        for key, values in self.BtoBMap.items():
            if len(values) > 0:
                b_to_b_entry = x.b.add()
                b_to_b_entry.parent_b = key
                b_to_b_entry.children_b.extend(values)

I have tried looping and using add and also tried append which I don' think is defined in proto2. extend doesn't work. How else can I assign these values?

Answer 1

With foo.proto:

syntax = "proto2";

message A {}
message B {}

message X {
  repeated A a = 1;
  repeated B b = 2;
}

A and B defined so the proto compiles.

You can:

import foo_pb2;

# Create parent
x = foo_pb2.X()

# Create children
a = foo_pb2.A()
b = foo_pb2.B()

# Either extend with (existing) children
x.a.extend([a,a])

# Or append with (existing) children
x.b.append(b)
x.b.append(b)

# Or add to create child(ren)
aa = x.a.add()
bb = x.b.add()

print(x)

Yields:

a {
}
a {
}
a {
}
b {
}
b {
}
b {
}