[Tutor] Dynamically changing a class

[Ricardo Aráoz]

Alan Gauld wrote:
> "Jason Doege" <jdoege at da-test.com> wrote
> 
>> I'd like to change the behavior of a class' member function 
>> dynamically
>> such that, once changed, all objects of the type would see the new
>> behavior.
> 
>>>>> class MyClass (object) :
>>      def mfunc(self, data):
>>        print 'pre change behavior'
>>
>>>>> aMyClassObj = MyClass()
>>>>> aMyClassObj.mfunc(data)
>> pre change behavior
>>>>> def MyClass.mfunc(self, data):  #this does not work :-(
>>      print 'post change behavior'
> 
> You need to do it thusly:
> 
> def newfunc(self, data):
>     print 'post change'
> MyClass.mfunc = newfunc
> 
> That seems to work.
> I'm slightly surprised since I didn't know if it would, but it seems 
> to!
> 

So lets take it a notch up.
Wanted to change the mfunc method but ONLY for an instance, not a class:

>>> MyObj = MyClass()
>>> MyObj.mfunc(data)
pre change behavior
>>> MyObj.mfunc = newfunc
>>> MyObj.mfunc(data)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: newfunc() takes exactly 2 arguments (1 given)

and this did not work (mfunc will ask for 2 parameters). So I tried :

>>> MyObj.mfunc = newfunc(MyObj)
Traceback (most recent call last):
  File "<input>", line 1, in <module>
NameError: name 'Myobj' is not defined

this didn't work either.

Any ideas?