PEP 277, Unicode file name support for Windows NT, Neil Hodgson
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Barry Warsaw
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@ -87,6 +87,7 @@ Index by Category
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S 274 Dict Comprehensions Warsaw
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S 275 Switching on Multiple Values Lemburg
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S 276 Simple Iterator for ints Althoff
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S 277 Unicode file name support for Windows NT Hodgson
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Finished PEPs (done, implemented in CVS)
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@ -235,6 +236,7 @@ Numerical Index
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S 274 Dict Comprehensions Warsaw
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S 275 Switching on Multiple Values Lemburg
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S 276 Simple Iterator for ints Althoff
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S 277 Unicode file name support for Windows NT Hodgson
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SR 666 Reject Foolish Indentation Creighton
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@ -265,6 +267,7 @@ Owners
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Giacometti, Frédéric B. fred@arakne.com
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Goodger, David dgoodger@bigfoot.com
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Griffin, Grant g2@iowegian.com
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Hodgson, Neil neilh@scintilla.org
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Hudson, Michael mwh@python.net
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Hylton, Jeremy jeremy@zope.com
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Kuchling, Andrew akuchlin@mems-exchange.org
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@ -0,0 +1,118 @@
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PEP: 277
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Title: Unicode file name support for Windows NT
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Version: $Revision$
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Last-Modified: $Date$
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Author: neilh@scintilla.org (Neil Hodgson)
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Status: Draft
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Type: Standards Track
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Created: 11-Jan-2002
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Python-Version: 2.3
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Post-History:
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Abstract
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This PEP discusses supporting access to all files possible on
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Windows NT by passing Unicode file names directly to the system's
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wide-character functions.
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Rationale
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Python 2.2 on Win32 platforms converts Unicode file names passed
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to open and to functions in the os module into the 'mbcs' encoding
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before passing the result to the operating system. This is often
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successful in the common case where the script is operating with
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the locale set to the same value as when the file was created.
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Most machines are set up as one locale and rarely if ever changed
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from this locale. For some users, locale is changed more often
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and on servers there are often files saved by users using
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different locales.
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On Windows NT and descendent operating systems, including Windows
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2000 and Windows XP, wide-character APIs are available that
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provide direct access to all file names, including those that are
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not representable using the current locale. The purpose of this
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proposal is to provide access to these wide-character APIs through
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the standard Python file object and posix module and so provide
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access to all files on Windows NT.
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Specification
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On Windows platforms which provide wide-character file APIs, when
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Unicode arguments are provided to file APIs, wide-character calls
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are made instead of the standard C library and posix calls.
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The Python file object is extended to use a Unicode file name
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argument directly rather than converting it. This affects the
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file object constructor file(filename[, mode[, bufsize]]) and also
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the open function which is an alias of this constructor. When a
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Unicode filename argument is used here then the name attribute of
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the file object will be Unicode. The representation of a file
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object, repr(f) will display Unicode file names as an escaped
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string in a similar manner to the representation of Unicode
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strings.
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The posix module contains functions that take file or directory
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names: chdir, listdir, mkdir, open, remove, rename, rmdir, stat,
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and _getfullpathname. These will use Unicode arguments directly
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rather than converting them. For the rename function, this
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behaviour is triggered when either of the arguments is Unicode and
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the other argument converted to Unicode using the default
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encoding.
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The listdir function currently returns a list of strings. Under
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this proposal, it will return a list of Unicode strings when its
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path argument is Unicode.
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To allow client code to determine that these features are
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implemented, the unicodefilenames function is provided. This
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function returns true when the underlying system supports file
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names containing most Unicode characters and any valid file name
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may be passed to open as a Unicode string.
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Restrictions
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On the consumer Windows operating systems, Windows 95, Windows 98,
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and Windows ME, there are no wide-character file APIs so behaviour
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is unchanged under this proposal. It may be possible in the
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future to extend this proposal to cover these operating systems as
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the VFAT-32 file system used by them does support Unicode file
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names but access is difficult and so implementing this would
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require much work. The "Microsoft Layer for Unicode" could be a
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starting point for implementing this.
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Python can be compiled with the size of Unicode characters set to
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4 bytes rather than 2 by defining PY_UNICODE_TYPE to be a 4 byte
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type and Py_UNICODE_SIZE to be 4. As the Windows API does not
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accept 4 byte characters, the features described in this proposal
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will not work in this mode so the implementation falls back to the
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current 'mbcs' encoding technique.
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Reference Implementation
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An experimental implementation is available from
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http://scintilla.sourceforge.net/winunichanges.zip
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References
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[1] Microsoft Windows APIs
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http://msdn.microsoft.com/
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Copyright
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This document has been placed in the public domain.
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