New submission from Skip Montanaro <s...@pobox.com>: os.path.commonprefix returns the common prefix of a list of paths taken character-by-character. This can return invalid paths. For example, os.path.commonprefix(["/export/home/dave", "/etc/passwd"]) will return "/e", which likely has no meaning as a path, at least in the context of the input list.
Ideally, os.path.commonprefix would operate component-by-component, but people rely on the existing character-by-character operation, so it has been so far impossible to change semantics. There are several possible ways to solve this problem. One, change how commonprefix behaves. Two, add a flag to commonprefix to allow it to operate component-by-component if desired. Three, add a new function to os.path. I personally prefer the first option. Aside from the semantic change though, it presents the problem of where to put the old definition of commonprefix. It's clearly of some use or people wouldn't have co- opted it for non-filesystem use. It could go in the string module, but that's been living a life in limbo since the creation of string methods. People have been loathe to add new functionality there. The second option seems to me like would just be a hack on top of already broken behavior and probably require the currently slightly broken behavior as the default to boot, so I won't go there. Since option one is perhaps not going to be available to me, I've implemented the third option as a new function, commonpathprefix. See the attached patch. It includes test cases and documentation changes. ---------- components: Library (Lib) files: cpp.diff keywords: needs review, patch, patch messages: 78338 nosy: skip.montanaro severity: normal stage: patch review status: open title: Common path prefix type: behavior versions: Python 3.1 Added file: http://bugs.python.org/file12469/cpp.diff _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue4755> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
