Question

The program prints Expired the first time. I am expecting the code to print “not expired” for atleast 4 times before printing expired. Can someone please explain the reason and help me correct the code. Thank you

import time
TIMEOUT =  5

class Timer ():
    def __init__(self):
        self.timeout = time.time()+TIMEOUT
    def isExpired ():
        return time.time() > self.timeout

timing = Timer()

def main():
    while 1:
        if timing.isExpired:
            print "Expired"
            return
        else:
            print "Not expired"
            print "sleeping for 1 second"
            time.sleep(1)

if __name__== "__main__":
    main()

Answer 1

You have several problems:

1. You did not give your isExpired method a self argument. Define it as def isExpired(self):.

2. You are creating a new Timer instance on each loop iteration. Move the timing = Timer() outside the while loop.

3. timing.isExpired is a reference to the method object iself (which is always true in a boolean context). You need to do timing.isExpired() to actually call it.

These are all basic Python issues that have nothing to do with Timer. Read the Python tutorial to learn how to use classes and so on.