On Fri, Mar 3, 2017 at 11:01 AM, Sven R. Kunze <srku...@mail.de> wrote:
> I wonder if those arguing against it also think dicts should not have item
> access:
>
> a[0]
>
> dict or list? Why should it matter?
>
Because a mapping that happens to have an integer key is a fundamentally
different thing than a sequence. It seems to me that in some of the
examples given, the use case really calls for a
mapping-with-integers-as-keys, rather than a sequence -- in which case, you
could use that, and have the get() :-)
And then you could iterate through it the same way, too!
you could get closer to sequence behvior by used a OrderedDict -- or maybe
even write a SortedDict that would keep the keys in order regardless of
when they were added.
> a.get(0, 'oops')
> Doesn't look so different to me.
>
but you are going to have issue with other things anyway, notable:
for thing in a:
# is thing a key or a value?????
- Which of the existing things (slice + [default], conditional on a slice,
> conditional on a len() call) do you think is the obvious way to do it?
>
> I think conditional on a len() call is the way to go -- it captures the
concept well -- sequences have a certain number of items -- how many this
one has is the question at hand. mapping, however, also have a certain
number of items, but the number does not indicate which ones are "missing".
I guess that's the key point for me -- in all teh examples I seen posed
(like parsing args) the sequence may contain from n to n+m items, but a
get() doesn' really solve your problem, because the default is probably
different depending on how MANY of the possible items are "missing".
So get(0 is only helpful if:
1) there is only one possible missing item
2) all the missing items have the same default -- unless that default is
sometign like None, in which case you are simply replacing one way to
express missing with another, I can't see that being common.
So I would expect to see a Sequence /get(0 be used to slightly clean up the
code that adds a bunch of Nones to sequences to make them all the same
length -- which is actually pretty easy to do anyway:
seq = seq + [None] * full_len - len(seq)
-CHB
--
Christopher Barker, Ph.D.
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