Why I can't extend bool in Python?
boolean, python, restriction
Solution
Guido's take on it:
I thought about this last night, and realized that you shouldn't be allowed to subclass bool at all! A subclass would only be useful when it has instances, but the mere existance of an instance of a subclass of bool would break the invariant that True and False are the only instances of bool! (An instance of a subclass of C is also an instance of C.) I think it's important not to provide a backdoor to create additional bool instances, so I think bool should not be subclassable.
Reference: http://mail.python.org/pipermail/python-dev/2002-March/020822.html
Problem
``` >>> class BOOL(bool): ... print "why?" ... why? Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: Error when calling the metaclass bases type 'bool' is not an acceptable base type ``` I thought Python trusted the programmer.