[issue21978] Support index access on OrderedDict views (e.g. o.keys()[7])

[Ram Rachum]

New submission from Ram Rachum:

Implement `__getitem__` on `OrdredDict.keys`, `OrdredDict.values` and `OrdredDict.items`, so the following code snippet wouldn't error:

    >>> from collections import OrderedDict
    >>> o = OrderedDict(((1, 2), (3, 4), (5, 6)))
    >>> o
    OrderedDict([(1, 2), (3, 4), (5, 6)])
    >>> o.keys()
    KeysView(OrderedDict([(1, 2), (3, 4), (5, 6)]))
    >>> o.keys()[0]
    Traceback (most recent call last):
      File "<string>", line 1, in <fragment>
    builtins.TypeError: 'KeysView' object does not support indexing
    >>> o.values()[0]
    Traceback (most recent call last):
      File "<string>", line 1, in <fragment>
    builtins.TypeError: 'ValuesView' object does not support indexing
    >>> o.items()[0]
    Traceback (most recent call last):
      File "<string>", line 1, in <fragment>
    builtins.TypeError: 'ItemsView' object does not support indexing

----------
components: Library (Lib)
messages: 223006
nosy: cool-RR
priority: normal
severity: normal
status: open
title: Support index access on OrderedDict views (e.g. o.keys()[7])
versions: Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21978>
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