Convert string to Python class object?

Given a string as user input to a Python function, I’d like to get a class object out of it if there’s a class with that name in the currently defined namespace. Essentially, I want the implementation for a function which will produce this kind of result:

class Foo:
    pass

str_to_class("Foo")
==> <class __main__.Foo at 0x69ba0>

Is this, at all, possible?