import sys

def str2Class(str):
    return getattr(sys.modules[__name__], str)
    
class Foo():
    def some_method():
        pass
    
class Bar():
    def some_other_method(self):
        class_name = "Foo"
        result = str2Class(class_name)
        print result
        
bar = Bar()
bar.some_other_method()