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Mon Nov 24 19:40:00 EST 2003 · https://mail.python.org/pipermail/python-dev/2003-November/040424.html

Hi everyone. My first post to the list, even thought I have been reading 
it for a long time now. 8)

Edward Loper wrote:

> Guido van Rossum wrote:
> > I'm curious about the use case that makes you feel the need for speed.
> > I would expect most properties not to simply redirect to another
> > attribute, but to add at least *some* checking or other calculation.
>
> The primary motivation was actually to make the code "easier to read"; 
> the speed boost was an added bonus.  (Though not a trivial one -- I do 
> have a good number of fairly tight loops that access properties.)  The 
> use case that inspired the idea is defining read-only properties for 
> immutable objects.  But I guess I would be better off going with 
> wrapper functions that create the read-only properties for me (like 
> <http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/157768>).

Actually, this would introduce a nice feature: allow to easily subclass 
the functions that are part of the property, without the need to 
re-create the property in the subclass.

class C(object):

    def get_foo(self):
        return 'C.foo'

    c = property('get_foo')

class D(object):

    def get_foo(self):
        return 'D.foo'

In the current behaviour, D would have to recreate the property, which 
can be cumbersome if you're only interested in overwriting one of the 
property's methods (which is the common case in my experience).

But I don't agree with Edward that property should accept strings. I 
think they should just accept functions as of now, but don't store the 
actual function object, just it's name, and delay the name lookup until 
it is actually needed.

What you guys think?

Regards,
Nicodemus.

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[Python-Dev] string-valued fget/fset/fdel for properties