Hello all,
I am playing around w/ Python's object system and decorators and I
decided to write (as an exercise) a decorator that (if applied to a
method) would call the superclass' method of the same name before
doing anything (initially I wanted to do something like CLOS
[1] :before and :end methods, but that turned out to be too
difficult).
However, I cannot get it right (specially, get rid of the eval). I
suspect that I may be misunderstanding something happening between
super objects and __getattribute__ methods.
Here's my code:
def endmethod(fun):
"""Decorator to call a superclass' fun first.
If the classes child and parent are defined as below, it should
work like:
>>> x = child()
>>> x.foo()
I am parent's foo
I am child's foo.
"""
name = fun.__name__
def decorated(self, *args, **kwargs):
try:
super_object = super(self.__class__, self)
# now I want to achieve something equivalent to calling
# parent.foo(*args, **kwargs)
# if I wanted to limit it only to this example
# this doesn't work: in the example, it calls child's foo,
# entering in an eternal loop (instead of calling parent's
# foo, as I would expect).
# super_object.__getattribute__(name)(*args, **kwargs)
# this does work, but I feel it's ugly
eval('super_object.%s(*args, **kwargs)' % name)
except AttributeError:
pass # if parent doesn't implement fun, we don't care
# about it
return fun(self, *args, **kwargs) # hopefully none
decorated.__name__ = name
return decorated
class parent(object):
def foo(self):
print 'I am parent\'s foo'
class child(parent):
@endmethod
def foo(self):
print "I am foo\'s foo."
if __name__=='__main__':
x = child()
x.foo()
Can anybody tell me how to call a superclass method knowing its name?
Thanks in advance,
-- Richard
[1] http://en.wikipedia.org/wiki/Common_Lisp_Object_System
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