Python equivalent of Ruby's 'method_missing'

Question

What is Python\'s equivalent of Ruby\'s method_missing method? I tried using __getattr__ but this hook applies to fields too. I only want to interc

Answer 1

Although I don't recommend it!!!!!!!!!!!!!!!!!!!!!

this sort of comes closer to implementing the behavior of calling the special method for every name that does not correspond to a callable attribute/method. Of course they still don't really have separate namespaces so it may feel a bit weird. It works by overriding __getattribute__ which works at a lower level then __getattr__ it tries to fetch an attribute if it fails it returns a curried special method to call with the name you called it with, if it succeeds it passes it on if its callable otherwise it wraps the result with a proxy object which acts in almost exactly the same way afterwards except it implements call with your special method.

It doesn't allow you to access the calling object because I couldn't think of a good way to do that without sort of leaking memory(the calling object) if it's already a non-callable attribute which you store(the only think I can think of is to start a new thread that deletes it after a minute, by then you have presumably called it unless you are using it in a closure which wouldn't be supported in that case).

Edit: I forgot callable may have some false positives.

depends on the http://pypi.python.org/pypi/ProxyTypes library

from peak.util.proxies import ObjectWrapper
from functools import partial

def m(name, *args, **kwargs):
    print(name,repr(args),repr(kwargs))


class CallProxy(ObjectWrapper):
   def __init__(self, obj, m, method_name):
       ObjectWrapper.__init__(self, obj)
       object.__setattr__(self, "_method_name", method_name)
       object.__setattr__(self, "_m", m)

   def __call__(self, *args, **kwargs):
       return self._m(self._method_name, *args,**kwargs)


class Y(object):
   def __init__(self):
       self.x = [3]
   def __getattribute__(self, name):
       try:
           val = object.__getattribute__(self, name)
           if not callable(val):
               return CallProxy(val, m, name)
           else:
               return val
       except AttributeError:
           return partial(m, name)

---

In [2]: y=Y()

In [3]: y.x
Out[3]: [3]

In [4]: y.z
Out[4]: 

In [5]: y.zz([12])
('zz', '([12],)', '{}')

In [6]: y.x.append(5)

In [7]: y.x
Out[7]: [3, 5]

In [8]: y.x(1,2,3,key="no")
('x', '(2, 3)', "{'key': 'no'}")