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

Edward Loper edloper at gradient.cis.upenn.edu
Mon Nov 24 04:35:33 EST 2003

Guido van Rossum wrote:
>>     1. It's easier to read.  (In my opinion, anyway; what do other
>>        people think?)
> Only if you're used to the new syntax.  Otherwise it could mean a
> costly excursion into the docs.
 > [...]
 >>     - It's one more special case to document/know.
 > Right.  It feels like a hack.

To me it seems like the "obvious" behavior for a string fget/fset/fdel, 
but if it's not universally obvious than you're proably right that it's 
a bad idea to add it.

> but I've got a suspicion you want to combine some string argument
> (most likely for fget) with some function argument.

Yes, the idea was that some properties only redirect on read, or only on 
write; and that the syntax could be made "cleaner" for those cases.

 > 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 

Thanks for the feedback!


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