andrew cooke wrote:
Andre Engels wrote:
On Wed, Mar 25, 2009 at 4:21 PM, andrew cooke <and...@acooke.org> wrote:
i will go against the grain slightly and say that "len" is probably the
best compromise in most situations (although i admit i don't know what
[...]
but i may be wrong - are there any containers (apart from pathological
hand-crafted examples) that would not define __len__()?
When writing my answer, I thought of generators, but I now find that
those will have boolean value 'true' whether or not they have
something to generate, so they will go wrong under either method. The
same holds for iterators. So for now I can't find any good example.
actually, the implication of what you said is probably worth emphasising
to the original poster: often you don't need to test whether a list is
empty or not, you simply iterate over its contents:
for x in foo:
# do something
this will then work with lists, tuples, sets, but also with iterators and
generators (which would give incorrect results in a test). in all cases,
"do something" will not happen if there are no data to process.
Now it would be nice to allow iteration over others too, like None .
a = None
for item in a :
do_something_with_item
I created a Null object for that, but that gives all kind of problems
with i.e. configobj.
cheers,
Stef
andrew
--
http://mail.python.org/mailman/listinfo/python-list
--
http://mail.python.org/mailman/listinfo/python-list
