Regexp syntax change in 1.6?

[Adam Sampson]

Hiya.

Under Python 1.5.2, I had a script containing the following line:

m = re.match(r"[a-z0-9]*://[^/]+/.*\.([^.#\?/]*)([#\?]?.*)?", url)

(Bonus points for guessing what it does; answer down the bottom.)
Under 1.6, this fails with:

[...]
  File "/usr/local/lib/python1.6/sre.py", line 44, in match
    return _compile(pattern, flags).match(string)
  File "/usr/local/lib/python1.6/sre.py", line 102, in _compile
    raise error, v # invalid expression
sre_constants.error: nothing to repeat 

I can narrow it down to:

>>> import re
>>> m = re.match(r"(x?)?", url)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/local/lib/python1.6/sre.py", line 44, in match
    return _compile(pattern, flags).match(string)
  File "/usr/local/lib/python1.6/sre.py", line 102, in _compile
    raise error, v # invalid expression
sre_constants.error: nothing to repeat 

whereas:

>>> m = re.match(r"(x?.)?", url)

works fine. Is this correct behaviour for SRE, or am I just being stupid?
"(x?)?" looks like a perfectly reasonable Perl-style regexp to me (and Perl
too)...

[Same question sent to python-help, before I remembered that my Usenet
connection actually works now.]

-- 

Adam Sampson
azz at gnu.org




[ The regexp extracts the extension of the file specified in a URL. ]