How to code dynamically created methods?

[Jay Loden]

kj wrote:
> 
> I've tried a bazillion ways to code dynamically generated methods,
> to no avail.
> 
> The following snippet is a very simplified (and artificial) demo
> of the problem I'm running into, featuring my latest attempt at
> this.  The idea here is to use __getattr__ to trap any attempt to
> invoke a nonexistent method, have it return a generic handler called
> _auto which creates the new method dynamically, invokes it, and
> "installs" it in the class, so that subsequent calls to the same
> method go directly to the newly created method, instead of to
> __getattr__.  It is this last step, the "installation" of the new
> method, that is giving me problems.
> 
> 
> class A( object ):
>     def __getattr__( self, name ):
>         self._auto_name = name
>         return self._auto
> 
>     def hello( self, name ):
>         print "hi! my name is %s" % name
>         
>     def _auto( self, *args ):
>         name = self._auto_name
>         def m( self, *args ): self.hello( name )
>         m( self, *args )
> 
>         m = classmethod( m )
>         setattr( A, name, m )
> 
> x = A()
> x.foo()  # ok
> x.foo()  # bombs
> 

I tried to do the same exact thing recently and got my answer from the mailing list. Here's the test code I got working using the help from the list:

#!/usr/bin/python

import functools

class TestClass:
  def __init__(self):
    pass

  def __getattr__(self, name):
    try:
      return getattr(self.__class__, name)
    except AttributeError:
      return functools.partial(self.foo, name)

  def foo(self, name, **args):
    print name
    for i in args:
      print " %s=%s" % (i, args[i])

  def bar(self):
    print "bar()"

test = TestClass()
test.someMethod()
test.anotherMethod()
test.someMethod()
test.bar()

Hope that helps,

-Jay