Magic method __str__

[nilamo]

But now I need to create a copy of this list, since I need to call this method later again

You should be able to call str(the_object) an infinite number of times, and not have any data change. If you're copying lists inside the __str__ function, you're doing something horribly wrong. Please, share some code, instead of giving tiny little glimpses of what might be lurking under the surface of your code.