[Tutor] Simple Thread Program not working (Newbie: Python)

[karthik Guru]

hello all,

Am not sure why am getting the errors at the specified place ( I have pasted
the error on those lines)
Can someone help.
---------------

import threading, time

class Test:
    def __init__(self):
        self.data = "start"
    def change(self,data):
        self.data = data
    def __str__(self):
        return self.data
    def __repr__(self):
        return self.data

class ChangeThread(threading.Thread):
    def __init_(self,val,a):
        self.ref = a
        threading.Thread.__init__(None,self)
    def run(self):
        count = 1
        while 1:
            self.ref.change(s,count) # AttributeError: ChangeThread instance
has no attribute 'ref'
            count+=1
            time.sleep(1)

class WatchThread(threading.Thread):
    def __init_(self,val,a):
        self.ref = a
        threading.Thread.__init__(None,self)
    def run(self):
        while 1:
            print 'changed data : ' + self.ref.data   # AttributeError:
#ChangeThread instance has no attribute 'ref'
            time.sleep(3)


def execute():
    print 'Start execute'
    t = Test()
    t1 = WatchThread(None,t)
    t2 = WatchThread(None,t)
    t3 = WatchThread(None,t)
    t1.start()
    t2.start()
    t3.start()
    time.sleep(2)

    t4 = ChangeThread(None,t)
    t4.start()

if __name__ == '__main__':
    execute()



This is the trace:

Start execute
Exception in thread Thread-1:
Traceback (most recent call last):
  File "d:\python21\lib\threading.py", line 378, in __bootstrap
    self.run()
  File "thread1.py", line 30, in run
    print 'changed data : ' + self.ref.data
AttributeError: WatchThread instance has no attribute 'ref'

Exception in thread Thread-2:
Traceback (most recent call last):
  File "d:\python21\lib\threading.py", line 378, in __bootstrap
    self.run()
  File "thread1.py", line 30, in run
    print 'changed data : ' + self.ref.data
AttributeError: WatchThread instance has no attribute 'ref'

Exception in thread Thread-3:
Traceback (most recent call last):
  File "d:\python21\lib\threading.py", line 378, in __bootstrap
    self.run()
  File "thread1.py", line 30, in run
    print 'changed data : ' + self.ref.data
AttributeError: WatchThread instance has no attribute 'ref'

Exception in thread Thread-4:
Traceback (most recent call last):
  File "d:\python21\lib\threading.py", line 378, in __bootstrap
    self.run()
  File "thread1.py", line 20, in run
    self.ref.change(s,count)
AttributeError: ChangeThread instance has no attribute 'ref'



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