This following post was originally posted to the wrong thread.
I am reposting (hopefully correctly) with the first and very
succint response. I thing the answer is a revealation to
be noted:
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On Tue, Mar 15, 2011 at 8:00 PM, Tim Johnson <t...@johnsons-web.com> wrote:
What is the difference between using
hasattr(object, name)
and
name in dir(object)
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Wayne Werner <waynejwer...@gmail.com> Replied:
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hasattr is basically
try:
object.name
return True
except AttributeError:
return False
while "name in dir(object)" is (AFAIK) more like:
for attr in dir(object):
if name == attr: return True
return False
However, rare is the occasion that you should use either of these. If you're
doing something like:
if hasattr(myobj, 'something'):
myobj.something()
else:
print "blah blah blah"
then what you really should be doing is:
try:
myobj.something()
except AttributeError:
print "blah blah blah"
because 1) you avoid the overhead of an extra(?) try-except block, 2) in
Python it's EAFP - Easier to Ask Forgivness than Permission, 3) You
shouldn't inspect an object to find out what it can do, you should just try
it and then handle failures appropriately (at least that's what I've been
told).
YMMV, objects in mirror are closer than they appear, etc. etc.
HTH,
Wayne
--
Tim
tim at johnsons-web dot com or akwebsoft dot com
http://www.akwebsoft.com
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