[Python-Dev] PEP 463: Exception-catching expressions

Antoine Pitrou solipsis at pitrou.net
Sat Feb 22 10:20:51 CET 2014

On Sat, 22 Feb 2014 16:12:27 +0900
"Stephen J. Turnbull" <stephen at xemacs.org> wrote:
> Note in support: I originally thought that "get" methods would be more
> efficient, but since Nick pointed out that "haveattr" is implemented
> by catching the exception (Yikes! LBYL implemented by using EAFP!), I
> assume that get methods also are (explicitly or implicitly)
> implemented that way.

Well, the only way to know that a key (or attribute) exists is to do
the lookup. What else would you suggest?

And, yes, EAFP can avoid race conditions and the like (besides being
more efficient with non-trivial keys).



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