[Python-Dev] Change in file() behavior in 2.5 (original) (raw)

Michael Urman murman at gmail.com
Thu Sep 7 15:37:41 CEST 2006

Hi folks,

Between 2.4 and 2.5 the behavior of file or open with the mode 'wU' has changed. In 2.4 it silently works. in 2.5 it raises a ValueError. I can't find any more discussion on it in python-dev than tangential mentions in this thread: http://mail.python.org/pipermail/python-dev/2006-June/065939.html

It is (buried) in NEWS. First I found: Bug #1462152: file() now checks more thoroughly for invalid mode strings and removes a possible "U" before passing the mode to the C library function. Which seems to imply different behavior than the actual entry: bug #967182: disallow opening files with 'wU' or 'aU' as specified by PEP 278.

I don't see anything in pep278 about a timeline, and wanted to make sure that transitioning directly from working to raising an error was a desired change. This actually caught a bug in an application I work with, which used an explicit 'wU', that will currently stop working when people upgrade Python but not our application.

Thanks, Michael

Michael Urman http://www.tortall.net/mu/blog

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