__getattr__ and recursion ?

[Stef Mientki]

hello,

I tried to find an easy way to add properties (attributes) to a number 
of different components.
So I wrote a class, from which all these components are derived.
By trial and error I created the code below, which now works, but
there is one thing I don't understand:
in the line indicated with "<<== 1" I'm not allowed to use

            for item in self.extra_getters :

because it will result in an infinite recursion.
But in the line indicated with "<<== 2" , I am allowed ...
... why is this allowed ??

thanks,
Stef Mientki


# ***********************************************************************
# ***********************************************************************
class _add_attribs ( object ) :
    def __init__ ( self ) :
        self.extra_setters = {}
        self.extra_getters = {}

    def _add_attrib ( self, text, setter = None, getter = None ) :
        if setter :
            self.extra_setters [ text ] = setter
        if getter :
            self.extra_getters [ text ] = getter

    # *********************************************************
    # always called instead of the normal mechanism
    # *********************************************************
    def __setattr__ ( self, attr, value ) :
        for item in self.extra_setters :
            if item == attr :
                self.extra_setters [ item ] ( value )
                break
        else :
            self.__dict__[attr] = value

    # *********************************************************
    # only called when not found with the normal mechanism
    # *********************************************************
    def __getattr__ ( self, attr ) :
        try :
            for item in self.__dict__['extra_getters'] :            <<== 1
                if item == attr :
                    return self.extra_getters [ item ] ( )          <<== 2
      except :
          return []
# ***********************************************************************