PEP 308: A PEP Writer's Experience - PRO

Erik Max Francis max at alcyone.com
Mon Feb 10 00:37:49 CET 2003


Paul Rubin wrote:

> I'm missing something--x and y both get evaluated in that example,
> so it's only a partial work around?

No, they don't.  Both the "and" and "or" operators implement
short-circuiting, so the single-element lists are only evaluated in the
eventuality that the expression gets that far:

>>> def f(): print 'f'
...  
>>> def g(): print 'g' 
... 
>>> (True and [f()] or [g()])[0]
f
>>> (False and [f()] or [g()])[0]
g

Not, of course, that I don't find the syntax abhorrent.

-- 
 Erik Max Francis / max at alcyone.com / http://www.alcyone.com/max/
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