You can feign immutablility on class attributes by playing with __setattr__. I don't remember the exact way to do it, but its roughly like this:

class YourClass:
    def __setattr__(self, name, value):
        if not hasattr(self, name):
            super().__setattr__(name, value)
       else:
            # handle as you wish if the
            # attr/value already exists.
            # pass, raise, whatever

I say "feign immutability" because there are still cases in which an attr value can change, such as:

• the underlying attribute contains a list and appending to the list
• the underlying attribute is a class and modifying the class's attributes
• pretty much anything that does "in place" changes, because so much of python is referential and has side effects.