When Closure get external variable's value?

[Huayang Xia]

What will the following piece of code print? (10 or 15)

        def testClosure(maxIndex) :

            def closureTest():
                return maxIndex

            maxIndex += 5

            return closureTest()

        print testClosure(10)

My question is when the closure function gets value for maxindex? Run
time or compile time?

Thanks.