[issue29853] Improve exception messages for remove and index methods

[Jim Fasarakis-Hilliard]

New submission from Jim Fasarakis-Hilliard:

Currently, there's a discrepancy in the exception reporting for the `.index` and `.remove` methods of many objects:

For arrays:

    array.remove(val) -> ValueError: array.remove(x): x not in list 
    array.index(val)  -> ValueError: array.index(x): x not in list

not only is always printing `x` not in list not informative, it's wrong since it isn't a list.

For tuples:

    tuple.index(val)  -> ValueError: tuple.index(x): x not in tuple

For lists:

    list.remove(val)  -> ValueError: list.remove(x): x not in list

list.index(val) produces a more informative message: ValueError: <val> is not in list

For deques:

    deque.remove(val) -> ValueError: deque.remove(x): x not in deque

similarly to lists, `deque.index(val)` prints the actual argument supplied.

I'm not sure if there's valid reasoning behind not providing the repr of the arguments in all `remove` methods but, if there isn't, I'd like to suggest changing all of them to use PyErr_Format and produce more informative messages:

    array.remove(val) -> ValueError: <val> is not in array 
    array.index(val)  -> ValueError: <val> is not in array
    tuple.index(val)  -> ValueError: <val> is not in tuple
    list.remove(val)  -> ValueError: <val> is not in list
    deque.remove(val) -> ValueError: <val> is not in deque

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messages: 289854
nosy: Jim Fasarakis-Hilliard
priority: normal
severity: normal
status: open
title: Improve exception messages for remove and index methods
type: enhancement
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29853>
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