New submission from Zack Weinberg <[email protected]>:
The documentation of the semantics of range expressions in regular expression
character classes is not precise enough. All it says is
Ranges of characters can be indicated by giving two characters and
separating them by a '-', for example [a-z] will match any lowercase ASCII
letter [... more examples, none involving non-ASCII characters]
In testing it seems that the behavior is simply to expand the range to a set of
characters by numeric code point, e.g. '[ᄀ-ፚ]' will match any single character
whose ord() is in between ord('ᄀ') and ord('ፚ') (inclusive). If that is the
intended behavior, I would like the documentation to explicitly say so. If
that is _not_ the intended behavior, I would like to know what the intended
behavior actually is, and for both the code and the documentation to be changed
to reflect the intent.
(I think expansion by numeric code point makes sense and is probably what most
existing programs want, but this is a contended issue in the context of POSIX
regular expressions, e.g. some C libraries try (not always successfully) to
make [0-9] match all of the characters that Python's \d matches, so it's not
"obvious".)
----------
assignee: docs@python
components: Documentation, Regular Expressions
messages: 321963
nosy: docs@python, ezio.melotti, mrabarnett, zwol
priority: normal
severity: normal
status: open
title: Nail down and document the behavior of range expressions in RE character
classes
type: behavior
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Python tracker <[email protected]>
<https://bugs.python.org/issue34156>
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