On Mon, Jun 29, 2020 at 9:12 PM Hans Ginzel <[email protected]> wrote:
>
> Tahnk you,
>
> On Fri, Jun 26, 2020 at 10:45:07AM -0700, Brett Cannon wrote:
> >Why can't you do `tuple(dict.items())` to get your indexable pairs?
>
> of course, I can.
> But how it is expensive/effective?
> What are the reasons, why object dict.items() is not subscriptable –
> dict.items()[0]?
>
>
Because dict is optimized for random access by key and iteration, but not for
random access by index.
For example:
sample 1:
items = [*d.items()]
for i in range(len(items)):
do(items[i])
sample 2:
for i in range(len(d)):
do(d.items()[i]) # if dict_items supports index access.
sample 1 is O(n) where n = len(d), but sample 2 is O(n^2).
By not supporting index access, dict_items prevents to write such
inefficient code.
--
Inada Naoki <[email protected]>
_______________________________________________
Python-ideas mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/[email protected]/message/KCCVM6PRXZPMTUQEKOF4VAG6ATS4XFSK/
Code of Conduct: http://python.org/psf/codeofconduct/
