[Python-Dev] PEP 8 addition: Preferred property style? (original) (raw)

Guido van Rossum guido at python.org
Thu Jan 22 15:11:11 EST 2004

currently, PEP 8 does not have any advice about the preferred style in defining properties. There are only two places in the standard library where they are used (socket.py and xml/dom/minicompat.py), so that doesn't provide much information either. Personally, I don't like the _namespace cluttering caused by defining _get, _set and/or del. Since I saw someone[0] on c.l.py using it, I always use this style:

def mtime(): doc = "Modification time" def get(self): return os.path.getmtime(str(self)) def set(self, t): return os.utime(str(self), (self.atime, t)) return get, set, None, doc mtime = property(*mtime()) I like it, because it's very readable for me, and doesn't clutter the namespace. Two questions about this style: - Is it tolerable to use it in the standard library (PrePEP)? - Should it be advised for or against in PEP 8, or neither?

I don't like it, and I'd rather not see this become a standard idiom.

Personally, I don't see the issue with the namespace cluttering (what's bad about it?) and I actually like that the getter/setter functions are also explicitly usable (hey, you might want to use one of these as the key argument to sort :-).

My objection against the def is that it requires a lot of sophistication to realize that this is a throw-away function, called just once to return argument values for the property call. It might also confuse static analyzers that aren't familiar with this pattern.

--Guido van Rossum (home page: http://www.python.org/~guido/)

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