Can a function access the instance of a class without using global in python?

Question

Why can I use the instance of a class in the following function without using globals?

class TestClass:
    def __init__(self, name):
        self.name = name
    def MyName(self):
        print "My name is: " + self.name

def testFunc():
    # why can I use the instance here?
    print "in testFunc()"
    instance.MyName()

if __name__ == '__main__':
    instance = TestClass("abc")
    print "in __main__"
    instance.MyName()

    testFunc()

Answer 1

In Python, globals are reachable by name from any scope. Your test_func() function can reference instance by name since it has been bound in global scope, namely in the if __name__ == '__main__' block.

The global keyword is useful for when you want to bind a global name from a local scope. To do so, you declare global foo and then bind it, e.g. foo = 1, from within the local scope.

Summarized: When referencing a global variable by name global is not required. When binding a global variable, global is required.