[Tim Peters]
>> Dang! I may have just found a use, in Zope's
>> lib/python/docutils/parsers/rst/directives/images.py (which is part
>> of docutils, not really part of Zope):
>>
>> figwidth = options.setdefault('figwidth')
>> figclass = options.setdefault('figclass')
>> del options['figwidth']
>> del options['figclass']
[David Goodger]
> If a feature is available, it *will* eventually be used!
> Whose law is that?
This is a different law, about design mistakes getting used by people
who should know better ;-)
> The code needs to store the values of certain dict entries, then
> delete them. This is because the "options" dict is passed on to
> another function, where those entries are not welcome. The code above
> is simply shorter than this:
>
> if options.has_key('figwidth'):
> figwidth = options['figwidth']
> del options['figwidth']
> # again for 'figclass'
>
> Alternatively,
>
> try:
> figwidth = options['figwidth']
> del options['figwidth']
> except KeyError:
> pass
Those wouldn't work in context, because they leave figwidth unbound if
it's not a key in options. Later code unconditionally references
fidgwidth.
> It saves between one line and three lines of code per entry. But
> since those entries are probably not so common, it would actually be
> faster to use one of the above patterns.
Changing
figwidth = options.setdefault('figwidth')
figclass = options.setdefault('figclass')
to
figwidth = options.setdefault('figwidth', None)
figclass = options.setdefault('figclass', None)
is a minimal semantics-neutral edit to avoid the unloved 1-argument case.
>> Assuming options is a dict-like thingie, it probably meant to do:
>>
>> figwidth = options.pop('figwidth', None)
>> figclass = options.pop('figclass', None)
> Yes, but the "pop" method was only added in Python 2.3. Docutils
> currently maintains compatibility with Python 2.1, so that's RIGHT
> OUT!
Oh, stop torturing yourself. Nobody uses Python 2.1 anymore ;-)
>> David, are you married to that bizarre use of setdefault <wink>?
> No, not at all. In fact, I will vehemently deny that I ever wrote
> such code, and will continue to do so until someone looks up its
> history and proves that I'm guilty, which I probably am.
No, I checked, and this code was actually added by an Asian spammer,
who polluted the docutils codebase with thousandsd of porn links
hidden in triple-quoted strings. Google reveals that 1-argument
setdefault() is a favorite of Asian porn spammers. So you should add
a second argument just to avoid getting in trouble with Interpol ;-)
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
