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

Matej Cepl mcepl at redhat.com
Thu Mar 7 11:08:40 CET 2013

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/fix_tests/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/fix_tests/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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