On May 2, 2006, at 8:42 PM, Daniel Miller wrote:
Oh, and use a try/except block rather than hasattr. It's more
pythonic... So with all those suggestions this is what we end up with:
def default_session(obj=None):
try:
return obj.__default_session__()
except AttributeError:
return _default_session(obj=obj)
if try/except were more "pythonic" than "hasattr", then python
shouldnt have an "hasattr" function. The try/except pattern is more
appropriate when the try: block will be called in almost all cases
and almost never the except: block, such as when the missing
attribute is initialized in the except: block so that it is only
called once. when the missing attribute is the norm, as it is in
this case since objects will only have a __session__ function in the
case of a certain configuration, the except: block adds a lot more
overhead than hasattr.
apparently, this is one of the oldest debates in the book:
http://mail.python.org/pipermail/python-list/2000-January/021450.html
but this doc should say it all:
http://docs.python.org/lib/node465.html
this example shows hasattr as about 3.6 times faster than try/except
for a missing attribute, whereas try/except is only 1.5 times faster
than hasattr for a present attribute (i tried it locally with py2.4
and got the same results).
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