On 4/19/2012 5:32 PM, Cameron Simpson wrote:
On 19Apr2012 14:32, Terry Reedy<tjre...@udel.edu> wrote:
| On 4/19/2012 11:51 AM, Jacob MacDonald wrote:
|> When I talk about an iterable, I say "iterable".
|
| Ditto.
I used to, but find myself saying "sequence" these days. It reads
better, but is it the same thing?
A Python 'sequence' is a collection that has a length and can be indexed
by counts 0, 1, ... . In other words, len(s) and s[n] work. This
definition is in the library manual somewhere. With those two, 'in',
'count', and 'index' and iteration are theoretically trivial. See 4.6.3.
Range Type but note that ranges were sequences before the 3.2 additions.
'Sequence' excludes all other iterables that do not have length and
count indexing: sets, dicts, iterators, files, and others, such as user
defined or extension tree structures. The point of the new iter/next
iterator protocol added in 2.2 was to expand the notion of iterable from
'sequence' or 'pseudo-sequence' to 'collection whose items can be
accessed one at a time' (whether or not the collection is linearly ordered).
The point of documenting an arg as 'iterable', when that is what the
function expects, is that is does not have to specifically be a sequence
or worse, a list. It is a wonderful freedom when the restriction is not
needed.
---
Terry Jan Reedy
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