Python Scoping Pitfalls

bad_scoping.py

class MyClass(object):
    def __init__(self):
        self.foo = "I'm the correct variable!"
    
    def do_something(self):
        #   Whoops, I forgot to write this as "self.foo".
        print foo
        
if __name__ == "__main__":
    foo = "Herp derp, I'm the wrong variable."
    MyClass().do_something()
    
#   This will print:
#       Herp derp, I'm the wrong variable.

good_scoping.py

class MyClass(object):
    def __init__(self):
        self.foo = "I'm the correct variable!"
    
    def do_something(self):
        #   Whoops, I forgot to write this as "self.foo".
        print foo
        
def main():        
    foo = "Herp derp, I'm the wrong variable."
    MyClass().do_something()
    
if __name__ == "__main__":
    main()
    
#   This will throw a NameError, as "foo" is not valid
#   in the scope of do_something on line 7.