[New-bugs-announce] [issue20426] Compiling a regex with re.DEBUG should force a recompile

[leewz]

New submission from leewz:

Compiling a regex with the `re.DEBUG` flag indicates that the user wants to see the debug output. `re.compile` is cached, though, so there is the possibility of no output.

Example:
import re
re.compile('1',re.DEBUG) #expected output
re.compile('1',re.DEBUG) #no output
re.compile('',re.DEBUG)  #no output (empty regex)

The workaround is to call `re.purge()`, which may remove other cached regexes that are still in use.

(Background: I wanted to check for equivalence of regexes, and a StackOverflow answer suggested comparing their `re.DEBUG`. http://stackoverflow.com/a/21398362/2963903)

----------
components: Regular Expressions
messages: 209595
nosy: ezio.melotti, leewz, mrabarnett
priority: normal
severity: normal
status: open
title: Compiling a regex with re.DEBUG should force a recompile
type: behavior
versions: Python 3.3

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue20426>
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