Strange error. MessageFactory object has no attribute GetMessageClass.

Pablo Camacho

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Jan 5, 2026, 8:49:43 AM Jan 5

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Hi,

I am trying to update python code to use a newer protobuf version: 6.33.2.

I replaced GetPrototype with GetMessageClass.

I get this error.
AttributeError: 'MessageFactory' object has no attribute 'GetMessageClass'

I believe that GetMessageClass is supposed to be defined in message factory since version 4. I am confused about why I get this error.

What else could be causing this error? What should I look into?

Also, the protobuf files were made with an older version of protobuf. Would there be problems with trying to use a newer version of protobuf to read protobuf files made by an older version of protobuf?

protoc version: libprotoc 33.1
python version: 3.10.12
protobuf version: 6.33.2.

Pablo Camacho

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Jan 5, 2026, 1:05:08 PM Jan 5

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More information on this error.

I am using a python virtual environment.

<path to virtual environment>/lib/python3.10/site-packages/google/protobuf/message_factory.py
Message Factory does exist in the python virtual environment.
GetMessageClass function is defined in the message_factory.py file.

```
def GetMessageClass(descriptor):
"""Obtains a proto2 message class based on the passed in descriptor.

Passing a descriptor with a fully qualified name matching a previous
invocation will cause the same class to be returned.

Args:
descriptor: The descriptor to build from.

Returns:
A class describing the passed in descriptor.
"""
concrete_class = getattr(descriptor, '_concrete_class', None)
if concrete_class:
return concrete_class
return _InternalCreateMessageClass(descriptor)

```

Pablo Camacho

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Jan 5, 2026, 1:44:21 PM Jan 5

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Solved!
I had to call the MessageFactory at module level instead of at instance/object level.

Solution

msg_class = message_factory.GetMessageClass(type_desc)

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