Overriding a method at the instance level on a subclass of a builtin type

[Aaron Brady]

On Dec 4, 11:16 am, "Zac Burns" <zac... at gmail.com> wrote:
> The class method seems to be the most promising, however I have more
> 'state' methods to worry about so I might end up building new classes
> on the fly rather than have a class per permutation of states! Now the
> code isn't quite as clear as I thought it was going to be.
>
> It seems unfortunate to me that methods are always looked up on the
> class for new style objects. Was this done for speed reasons?

I thought of two more solutions.  One, derive a new class for each
instance as you create it, and assign methods to that, that can be
shared.  Even more memory consumption though.

>>> class A:
...     def methA( self ): print 'methA'
...     def methB( self ): print 'methB'
...
>>> class A1(A): meth= A.methA
...
>>> a1=A1()
>>> a1.meth()
methA
>>> A1.meth=A.methB
>>> a1.meth()
methB

Two, use getter properties to return the right function, based on
index and array.

>>> class A( object ):
...     @property
...     def meth( self ):
...             return self.meths[ self.methA_i ].__get__( self, A )
...     def methA( self ):
...             print 'methA'
...             self.methA_i+= 1
...     def methB( self ):
...             print 'methB'
...             self.methA_i-= 1
...     meths= [ methA, methB ]
...     def __init__( self ):
...             self.methA_i= 0
...
>>> a= A()
>>> a.meth()
methA
>>> a.meth()
methB
>>> a.meth()
methA

Or (two B), look up the method by name on name-index pair.

>>> class A( object ):
...     @property
...     def meth( self ):
...             return getattr( self, self.meths[ self.methA_i ] )
...     def methA( self ):
...             print 'methA'
...             self.methA_i+= 1
...     def methB( self ):
...             print 'methB'
...             self.methA_i-= 1
...     meths= [ 'methA', 'methB' ]
...     def __init__( self ):
...             self.methA_i= 0
...
>>> a= A()
>>> a.meth()
methA
>>> a.meth()
methB
>>> a.meth()
methA

The 'meths' list will need separate lists for each 'group' of state-
dependent functions you wish to use.