PEP 308: A PEP Writer's Experience - PRO

[Samuele Pedroni]

"Paul Rubin" <phr-n2003b at NOSPAMnightsong.com> ha scritto nel messaggio
news:7xisvt9pv9.fsf at ruckus.brouhaha.com...
> Andrew Koenig <ark at research.att.com> writes:
> > Samuele> ife = lambda box: box[0]
> > Samuele> z = ife(cond and [x] or [y])
> >
> > Samuele> if Python had had a ternary cond op, I would never have seen
> > Samuele> that <sniff>.
> >
> > You're right -- that's about the nicest workaround I've seen.
>
> I'm missing something--x and y both get evaluated in that example,
> so it's only a partial work around?

and,or short-circuit

>>> def falseStr():
...   print "falseStr"
...   return ''
...
>>> def trueStr():
...   print "trueStr"
...   return "T"
...
>>> ife=list.pop
>>> def test(cond):
...   return ife(cond and [falseStr()] or [trueStr()])
...
>>> test(True)
falseStr
''
>>> test(False)
trueStr
'T'
>>> True and '' or 'T' # bad
'T'
>>>