[issue12170] index() and count() methods of bytes and bytearray should accept byte ints

[Petri Lehtinen]

Petri Lehtinen <petri at digip.org> added the comment:

Attached a patch with the following changes:

Allow an integer argument in range(0, 256) for the following bytes and
bytearray methods: count, find, index, rfind, rindex. Initially, only
count and index were targeted, but as index is implemented in a helper
function that is also used to implement find, rfind and rindex, these
functions were affected too.

The bytes methods were changed to use the new buffer protocol instead
of the deprecated PyObject_AsCharBuffer, for consistency with the
bytearray code.

Tests for all the modified functions were expanded to cover the new
functionality. While at it, the tests for count, index and rindex were
also further expanded (to test for slices, for example), as they were
initially quite minimal.

A paragraph describing the additional semantics of the five methods
was added to the documentation.

The error messages of index and rindex were left untouched
("substring not found" and "subsection not found"). In a case where
the first argument is an integer, the error messages could talk about
a byte instead of substring/subsection. This would have been a bit
non-straightforward to implement, so I didn't.

The docstrings were also left unchanged, as I couldn't find a good
wording for them. The problem is not that the first argument may now
be an integer, but as it can now be more than a substring or
subsection, we might have to specify what a substring or subsection
really means. And that explanation would be lengthy (because of the buffer protocol, that's not a concept that a regular Python programmer is, or even needs to be, familiar with)...

And finally, there's one thing that I'm unsure of:

When an integer out of range(0, 256) is passed as the first argument,
should we raise a ValueError or a TypeError? Currently, a ValueError
is raised, but this may be bad for index and rindex, as they raise a
ValueError when the substring or byte is not found. I made the
decision to raise a ValueError decision because __contains__ of both
bytes and bytearray raise a ValueError when passed an integer not in
range(0, 256).

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keywords: +needs review, patch
stage: test needed -> patch review
Added file: http://bugs.python.org/file22733/issue12170.patch

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