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Groups > comp.lang.python > #20388 > unrolled thread

re module: Nothing to repeat, but no sre_constants.error: nothing to repeat ?

Started byDevin Jeanpierre <jeanpierreda@gmail.com>
First post2012-02-13 23:38 -0500
Last post2012-02-14 08:33 -0500
Articles 3 — 2 participants

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  re module: Nothing to repeat, but no sre_constants.error: nothing to repeat ? Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-02-13 23:38 -0500
    Re: re module: Nothing to repeat, but no sre_constants.error: nothing to repeat ? Vinay Sajip <vinay_sajip@yahoo.co.uk> - 2012-02-14 05:20 -0800
      Re: re module: Nothing to repeat, but no sre_constants.error: nothing to repeat ? Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-02-14 08:33 -0500

#20388 — re module: Nothing to repeat, but no sre_constants.error: nothing to repeat ?

FromDevin Jeanpierre <jeanpierreda@gmail.com>
Date2012-02-13 23:38 -0500
Subjectre module: Nothing to repeat, but no sre_constants.error: nothing to repeat ?
Message-ID<mailman.5792.1329194327.27778.python-list@python.org>
Hey Pythonistas,

Consider the regular expression "$*". Compilation fails with the
exception, "sre_constants.error: nothing to repeat".

Consider the regular expression "(?=$)*". As far as I know it is
equivalent. It does not fail to compile.

Why the inconsistency? What's going on here?

-- Devin

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#20396

FromVinay Sajip <vinay_sajip@yahoo.co.uk>
Date2012-02-14 05:20 -0800
Message-ID<0cc200e6-6e4c-47b7-8563-3abc3ac94f22@k10g2000yqk.googlegroups.com>
In reply to#20388
On Feb 14, 4:38 am, Devin Jeanpierre <jeanpierr...@gmail.com> wrote:
> Hey Pythonistas,
>
> Consider the regular expression "$*". Compilation fails with the
> exception, "sre_constants.error: nothing to repeat".
>
> Consider the regular expression "(?=$)*". As far as I know it is
> equivalent. It does not fail to compile.
>
> Why the inconsistency? What's going on here?
>
> -- Devin

$ is a meta character for regular expressions. Use '\$*', which does
compile.

Regards,

Vinay Sajip

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#20397

FromDevin Jeanpierre <jeanpierreda@gmail.com>
Date2012-02-14 08:33 -0500
Message-ID<mailman.5798.1329226436.27778.python-list@python.org>
In reply to#20396
On Tue, Feb 14, 2012 at 8:20 AM, Vinay Sajip <vinay_sajip@yahoo.co.uk> wrote:
> $ is a meta character for regular expressions. Use '\$*', which does
> compile.

I mean for it to be a meta-character.

I'm wondering why it's OK for to repeat a zero-width match if it is a
zero-width assertion.

-- Devin

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