[docs] [issue29323] Wrong documentation (Library) for unicode and str comparison

RK-5wWm9h report at bugs.python.org
Thu Jan 19 09:40:31 EST 2017


New submission from RK-5wWm9h:

PROBLEM (IN BRIEF):
In the currently published 2.7.13 The Python Standard Library (Library Reference manual) section 5.6 "Sequence Types" (https://docs.python.org/2/library/stdtypes.html#sequence-types-str-unicode-list-tuple-bytearray-buffer-xrange):

    "to compare equal, ... the two sequences must be of the same type"

This an *incorrect (and misleading) statement*, for the unicode and str case.


PROPOSED FIX:

Current full paragraph:

    "Sequence types also support comparisons. In particular, tuples and lists are compared lexicographically by comparing corresponding elements. This means that to compare equal, every element must compare equal and the two sequences must be of the same type and have the same length. (For full details see Comparisons in the language reference.)"

Proposed replacement text:

    "Sequence types also support comparisons. In particular, tuples and lists are compared lexicographically by comparing corresponding elements. This means that to compare equal, every element must compare equal and the two sequences 
must be of the same type and have the same length. (Unicode and str are treated as the same type here; for full details see Comparisons in the language reference.)"


DETAILS, JUSTIFICATION, CORRECTNESS, ETC:

The current incorrect text is really misleading.

The behaviour that a str and a unicode object -- despite being objects of different types -- may compare equal, is explicitly stated in the 2.7.13 The Python Language Reference manual, section 5.9 "Comparisons" (https://docs.python.org/2/reference/expressions.html#comparisons):

    "* Strings are compared lexicographically using the numeric equivalents (the result of the built-in function ord()) of their characters. Unicode and 8-bit strings are fully interoperable in this behavior. [4]"

(Aside: Incidentally an earlier paragraph in the Language Ref fails to cover the unicode and str case; see separately filed bug Issue 29321.)

----------
assignee: docs at python
components: Documentation
messages: 285792
nosy: RK-5wWm9h, docs at python
priority: normal
severity: normal
status: open
title: Wrong documentation (Library) for unicode and str comparison
type: behavior
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29323>
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