Suggestion: make sequence and map interfaces more similar

[Chris Angelico]

On Thu, Mar 31, 2016 at 11:36 PM, Marko Rauhamaa <marko at pacujo.net> wrote:
> Chris Angelico <rosuav at gmail.com>:
>
>> On Thu, Mar 31, 2016 at 10:22 PM, Antoon Pardon
>> <antoon.pardon at rece.vub.ac.be> wrote:
>> Okay. I'll put a slightly different position: Prove that your proposal
>> is worth discussing by actually giving us an example that we can
>> discuss.
>
> Sorry for missing most of the arguments here, but if you are talking
> about treating lists as special cases of dicts, I have occasionally
> instinctively wanted something like this:
>
>     >>> fields = [ "x", "y", "z" ]
>     >>> selector = (1, 1, 0)
>     >>> list(map(fields.get, selector))
>     Traceback (most recent call last):
>     File "<stdin>", line 1, in <module>
>     AttributeError: 'list' object has no attribute 'get'
>
> Or course, I could:
>
>     >>> list(map(fields.__getitem__, selector))
>     ['y', 'y', 'x']
>
> but that would abuse a dunder method. So I will need to:
>
>     >>> list(map(lambda i: fields[i], selector))
>     ['y', 'y', 'x']
>
> or (most likely):
>
>     >>> new_fields = []
>     >>> for i in selector:
>     ...   new_fields.append(fields[i])
>     ...
>     >>> new_fields
>     ['y', 'y', 'x']
>
>
> This tiny problem of mine could be remedied by adding a get method to
> lists.

Or, even more likely and even more Pythonic:

>>> [fields[i] for i in selector]
['y', 'y', 'x']

As soon as you get past the easy and obvious case of an existing
function, filter and map quickly fall behind comprehensions in utility
and readability.

ChrisA