How to call Thread derived class method from run in Python?

Question

Currently I'm not a python programmer, but I'm giving some maintenance to some python code, and I have what's more or less the following:

class DerivedThread(threading.Thread):
  def __init__(self):
    threading.Thread.__init__(self)

  def initStuff():
    print "Hello 2"

  def run(self):
    print "Hello 1"
    self.initStuff()
    print "Hello 3"

initStuff does not call print in truth, just set some variables, I've added this method for organization, there was only __init__ and run before.

The problem is that, once execution reachs self.initStuff(), I see no messages following anymore, only "Hello 1", I thought it was some problem with calling derived methods with python, but I don't know what's happening.

What's happening?

Rostyslav Dzinko · Accepted Answer · 2012-08-11 21:08:21Z

4

The problem is in definition of your initStuff method. It requires at least one argument (usually called 'self') in it's definition (you've defined no arguments). Let's see what happens then:

class MyClass(object):

    def initStuff(self):
        pass

c = MyClass()
c.initStuff()

TypeError: initStuff() takes no arguments (1 given)

So obviously your code fails silently in thread you've defined.

The way to fix the problem is to define initStuff method following Python rules.

 ...
 def initStuff(self):  #  Here 'self' argument is defined
      pass

This kind of method is called instancemethod as it's called on behalf of your class instance (and the first argument is an instance object itself that must be explicitly defined).

Read more about classes in documentation.

answered Aug 11, 2012 at 21:08

Rostyslav Dzinko

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Comments

oblitum · Accepted Answer · 2012-08-25 17:12:49Z

1

Oh I got it, I just needed to pass self as argument to initStuff.

edited Aug 25, 2012 at 17:12

answered Aug 11, 2012 at 20:39

oblitum

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