[Python-Dev] Difference in RE between 3.2 and 3.3 (or Aaron Swartz memorial) (original) (raw)

Victor Stinner victor.stinner at gmail.com
Thu Mar 7 14:34:25 CET 2013


You should try to write a simple test not using your library (just copy/paste code) reproducing the issue. If you can do that, please fill an issue on bugs.python.org.

Victor

2013/3/7 Matej Cepl <mcepl at redhat.com>:

On 2013-03-06, 18:34 GMT, Victor Stinner wrote:

In short, Unicode was rewritten in Python 3.3 for the PEP 393. It's not surprising that minor details like singleton differ. You should not use "is" to compare strings in Python, or your program will fail on other Python implementations (like PyPy, IronPython, or Jython) or even on a different CPython version. I am sorry, I don't understand what you are saying. Even though this has been changed to https://github.com/mcepl/html2text/blob/fixtests/html2text.py#L90 the tests still fail. But, Amaury is right: the function doesn't make much sense. However, ... when I have “fixed it” from https://github.com/mcepl/html2text/blob/master/html2text.py#L95 def onlywhite(line): """Return true if the line does only consist of whitespace characters.""" for c in line: if c is not ' ' and c is not ' ': return c is ' ' return line to https://github.com/mcepl/html2text/blob/fixtests/html2text.py#L90 def onlywhite(line): """Return true if the line does only consist of whitespace characters.""" for c in line: if c != ' ' and c != ' ': return c == ' ' return line tests on ALL versions of Python are suddenly failing ... https://travis-ci.org/mcepl/html2text/builds/5288190 Curiouser and curiouser! At least, I seem to have the point, where things are breaking, but I have to admit that condition really doesn’t make any sense to me.

Anyway, you spotted a missed optimization: it's now "fixed" in Python 3.3 and 3.4 by the following commits. Well, whatever is the problem, it is not fixed in python 3.3.0 (as you can see in https://travis-ci.org/mcepl/html2text/builds/4969045) as I can see on my computer. Actually, good news is that it seems to be fixed in the master branch of cpython (or the tip, as they say in the Mercurial world). Any thoughts? Matěj


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