Adding method to object

Gonçalo Rodrigues op73418 at mail.telepac.pt
Wed Dec 3 13:02:37 CET 2003


On Wed, 03 Dec 2003 10:44:12 +0100, "Thomas Guettler"
<guettli at thomas-guettler.de> wrote:

>Hi!
>
>How can I add a method to an object.
>This code does not work:
>
>class Foo:
>    def __init__(self):
>        self.counter=0
>
>f=Foo()
>
>def incr(self):
>    self.counter+=1
>
>f.incr=incr
>
>f.incr()
>
>===> python extend.py
>Traceback (most recent call last):
>  File "extend.py", line 12, in ?
>    f.incr()
>TypeError: incr() takes exactly 1 argument (0 given)

You have to call it like

f.incr(f)

If you want to leave out the f as arg (call it like an instance
method) then

>>> import new
>>> help(new.instancemethod)
Help on class instancemethod in module __builtin__:

class instancemethod(object)
 |  instancemethod(function, instance, class)
 |  
 |  Create an instance method object.
 |  
...

And

new.instancemethod(incr, f, f.__class__)

Should do the trick.

With my best regards,
G. Rodrigues




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