[Tutor] Unbound methods

[François Granger]

At 2:10 +0200 21/11/02, in message [Tutor] Unbound methods, am@fx.ro wrote:
>Hello all!
>
>I am new to both python and this list.
>
>I am trying to write my first silly script containing a class
>with a few methods (this script might become someday a part
>of a WAV player):
>
>class WavSet:
>     def __init__(self):
>         print 'Init'
>     def open(self):
>         print 'Open'
>     def close(self):
>         print 'Close'
>     def play(self,wav_id):
>         print 'Play %d'%(wav_id,)
>
>w=WavSet
>print w.open()
>print w.close()
>
>I got an error that i don't understand:
>TypeError: unbound method must be called with class instance 1st argument

Python 2.2.2 (#138, Oct 25 2002, 23:10:42)  [CW CARBON GUSI2 THREADS GC] on mac
Type "copyright", "credits" or "license" for more information.
>>>  class WavSet:
     def __init__(self):
         print 'Init'
     def open(self):
         print 'Open'
     def close(self):
         print 'Close'
     def play(self,wav_id):
         print 'Play %d'%(wav_id,)

w=WavSet
print w.open()
print w.close()

... ... ... ... ... ... ... ... ... >>> >>> Traceback (most recent call last):
   File "<stdin>", line 1, in ?
TypeError: unbound method open() must be called with WavSet instance 
as first argument (got nothing instead)
>>>  Traceback (most recent call last):
   File "<stdin>", line 1, in ?
TypeError: unbound method close() must be called with WavSet instance 
as first argument (got nothing instead)
>>>  >>> w=WavSet()
Init
>>>  print w.open()
Open
None
>>>  print w.close()
Close
None
>>>

the line w=WavSet bind the name w to the WavSet class but does not 
create an instance of the class.
You could use w instead of WavSet anywhere.

The line w=WavSet() create an instance of WavSet and bind this 
instance to w. Then you can call methodes on w.

HTH
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