Timer runs only once.

[siva gnanam]

The following program print hello world only once instead it has to print the string for every 5 seconds.

    from threading import Timer;

    class TestTimer:

        def __init__(self):
            self.t1 = Timer(5.0, self.foo);

        def startTimer(self):
            self.t1.start();

        def foo(self):
            print("Hello, World!!!");

    timer = TestTimer();
    timer.startTimer();


                           (program - 1)

But the following program prints the string for every 5 seconds.

    def foo():
        print("World");
        Timer(5.0, foo).start();

    foo();
 
                            (program - 2)

Why (program - 1) not printing the string for every 5 seconds ?  And how to make the (program - 1) to print the string for every 5 seconds continuously.