Isaac Morland added the comment:
Maybe the issue is that I work with SQL constantly. In SQL, if I say "SELECT
a, b, c FROM t" and table t has columns a, b, c, d, e, f, I can still select a,
b, and c from the result. So to me it is natural that getting a bunch of
attributes returns something (row or object, depending on the context), where
the attributes are still labelled.
I understand why this was rejected as a universal change to attrgetter - in
particular, I didn't re-evaluate the appropriateness of the change once I
realized that attrgetter has a C implementation - but I don't understand why
this isn't considered a natural option to provide.
Using rename=True is just a way of having it not blow up if an attribute name
requiring renaming is supplied. I agree that actually using such an attribute
requires either guessing the name generated by the rename logic in namedtuple
or using numeric indexing. If namedtuple didn't have rename=True then I
wouldn't try to re-implement it but since it does I figure it's worth typing ",
rename=True" once - it's hardly going to hurt anything.
Finally as to use cases, I agree that if the only thing one is doing is sorting
it doesn't matter. But with groupby it can be very useful. Say I have an
iterator providing objects with fields (heading_id, heading_text, item_id,
item_text). I want to display each heading, followed by its items.
So, I groupby attrgetter ('heading_id', 'heading_text'), and write a loop
something like this:
for heading, items in groupby (source, attrgetter ('heading_id',
'heading_text')):
# display heading
# refer to heading.heading_id and heading.heading_text
for item in items:
# display item
# refer to item.item_id and item.item_text
Except I can't, because heading doesn't have attribute names. If I replace
attrgetter with namedattrgetter then I'm fine. How would you write this? In
the past I've used items[0] but that is (a) ugly and (b) requires "items =
list(items)" which is just noise.
I feel like depending on what is being done with map and filter you could have
a similar situation where you want to refer to the specific fields of the tuple
coming back from the function returned by attrgetter.
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue31086>
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