Is there a Data Type in Python which cannot be typecast in string

Question

Lets say 'a' is of some type (which I want to know!)

Doing a thing like:

b = str(a)

This should favorably raise a TypeError

Answer 1

There is no builtin Python class that raises a TypeError with str, but you could define a custom class:

class Foo(object):
    def __str__(self):
        raise TypeError('Can not by stringified')


foo = Foo()
b = str(foo)

raises a TypeError.