Timer runs only once in python

Question

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.

Why are you wrapping it in an extra class to begin with? Is this necessary? — deepbrook
– deepbrook, Commented Dec 1, 2016 at 15:29

jklemmack · Accepted Answer · 2016-12-01 15:49:19Z

1

(program - 2) prints a string every 5 seconds because it is calling itself recursively. As you can see, you call foo() function inside itself and this is the reason because it works.

If you want to print a string every 5 secs in (program - 1) using a class you could (but it's not really a good practice!):

from threading import Timer

class TestTimer:
    def boo(self):
        print("World")
        Timer(1.0, self.boo).start()

timer = TestTimer()
timer.boo()

edited Dec 1, 2016 at 15:49

jklemmack

3,6363 gold badges35 silver badges59 bronze badges

answered Nov 30, 2016 at 15:53

Fabrizio A.

641 silver badge8 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

deepbrook · Accepted Answer · 2016-12-01 15:39:49Z

0

As has been pointed out, you're calling the foo() recursively:

def foo():
    print("World");
    Timer(5.0, foo).start();  # Calls foo() again after 5s and so on

foo();

In your question, you've created a wrapper around threading.Timer - I suggest you simply subclass it:

from threading import Timer

class TestTimer(Timer):

    def __init__(self, i):
        self.running = False
        super(TestTimer, self).__init__(i, self.boo)

    def boo(self):
        print("Hello World")

    def stop():
        self.running = False
        super(TestTimer, self).stop()

    def start():
        self.running = True
        while self.running:
            super(TestTimer, self).start()

t = TestTimer(5)
t.start()

edited Dec 1, 2016 at 15:39

answered Dec 1, 2016 at 15:32

deepbrook

2,6864 gold badges32 silver badges51 bronze badges

Collectives™ on Stack Overflow

Timer runs only once in python

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related