What’s an example use case for a Python classmethod?

I’ve read What are Class methods in Python for? but the examples in that post are complex. I am looking for a clear, simple, bare-bones example of a particular use case for classmethods in Python.

Can you name a small, specific example use case where a Python classmethod would be the right tool for the job?

Answer

Helper methods for initialization:

class MyStream(object):

    @classmethod
    def from_file(cls, filepath, ignore_comments=False):    
        with open(filepath, 'r') as fileobj:
            for obj in cls(fileobj, ignore_comments):
                yield obj

    @classmethod
    def from_socket(cls, socket, ignore_comments=False):
        raise NotImplemented # Placeholder until implemented

    def __init__(self, iterable, ignore_comments=False):
       ...