Multiple inheritance along with threading in python

Question

I have a code sample which is very similar to following

import threading
import datetime
import time
import sys

class FirstClass(object):
    def __init__(self):
        print 'initialized'

class ThreadClass(FirstClass, threading.Thread):
    def __init__(self):
        super(ThreadClass, self).__init__()
        print 'initialized2'

    def run(self):
        time.sleep(1)
        now = datetime.datetime.now()
        sys.stdout.write("%s says Hello World at time: %s \n" % (self.getName(), now))

for i in range(20):
    t = ThreadClass()
    t.start()

Due to call-next-method of python I am not able to run init method of both FirstClass and thread. Is there any alternate way through which I can solve this issue.

Answer 1

You'll need to call super(FirstClass, self).__init__() in the FirstClass.__init__() initializer too.

The whole point of using super() is to make passing on the call to a parent cooperative. In your specific MRO FirstClass is listed before threading.Thread, so without explicitly calling the next __init__ in MRO order threading.Thread.__init__() never gets invoked.

You may want to look at the excellent PyCon 2015 presentation by Raymond Hettinger on how super() works in this context.