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From: Marko Rauhamaa <marko@pacujo.net>
Newsgroups: comp.lang.python
Subject: Re: Suggestion: make sequence and map interfaces more similar
Date: Thu, 31 Mar 2016 15:36:24 +0300
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Chris Angelico <rosuav@gmail.com>:

> On Thu, Mar 31, 2016 at 10:22 PM, Antoon Pardon
> <antoon.pardon@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'

analogously with:

    >>> field_dict = { 0: "x", 1: "y", 2: "z" }
    >>> list(map(field_dict.get, selector))
    ['y', 'y', 'x']

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.


Marko