"Aliasing" an object's __str__ to a different method

[Jeffrey E. Forcier]

I am attempting to write a class whose string representation changes  
in response to external stimuli. While that effect is obviously  
possible via other means, I attempted this method first and was  
surprised when it didn't work, so I now want to know why :)

Given the following class definition:

class MyClass(object):

         def Edit(self):
                 return "I, %s, am being edited" % (self)

         def View(self):
                 return "I, %s, am being viewed" % (self)

         def setEdit(self):
                 self.__str__ = self.__repr__ = self.Edit

         def setView(self):
                 self.__str__ = self.__repr__ = self.View


...I would expect the following behavior:

In [130]: testObject = MyClass()
In [131]: testObject.setEdit()
In [132]: str(testObject)
Out[132]: 'I, <__main__.MyClass object at 0x511270>, am being edited'


Unfortunately, this is what happens instead:

In [130]: testObject = MyClass()
In [131]: testObject.setEdit()
In [132]: str(testObject)
Out[132]: '<__main__.MyClass object at 0x511270>'


In other words, str() is _NOT_ apparently calling <object>.__str__ as  
it's supposed to! However, calling __str__ directly (which, yes,  
you're not supposed to do) does work as expected:

In [133]: testObject.__str__()
Out[133]: 'I, <__main__.MyClass object at 0x511270>, am being edited'


Now, my understanding is that functions/methods are first-order  
objects, and can be pointed to via reference, and that appears to be  
true:

In [135]: def func1():
    .....:     print "I'm func1"
    .....:
In [136]: def func2():
    .....:     print "I'm func2"
    .....:
In [137]: func2 = func1
In [138]: func2()
I'm func1


However, expressions such as self.__str__ = <some function or method>  
aren't working for me, as above. Why not?

Thanks for any responses,
Jeff

--
Jeffrey E. Forcier
Junior Developer, Research and Development
Stroz Friedberg, LLC
15 Maiden Lane, 12th Floor
New York, NY 10038
[main]212-981-6540 [direct]212-981-6546
http://www.strozllc.com

This message is for the named person's use only.  It may contain
confidential, proprietary or legally privileged information. No right to
confidential or privileged treatment of this message is waived or lost
by any error in transmission.  If you have received this message in
error, please immediately notify the sender by e-mail or by telephone at
212.981.6540, delete the message and all copies from your system and
destroy any hard copies.  You must not, directly or indirectly, use,
disclose, distribute, print or copy any part of this message if you are
not the intended recipient.