[Python-Dev] PEP 383: Non-decodable Bytes in System Character Interfaces (original) (raw)

Barry Scott barry at barrys-emacs.org
Thu Apr 30 23:13:43 CEST 2009

On 30 Apr 2009, at 21:06, Martin v. Löwis wrote:

How do get a printable unicode version of these path strings if they contain none unicode data?

Define "printable". One way would be to use a regular expression, replacing all codes in a certain range with a question mark. What I mean by printable is that the string must be valid unicode that I can print to a UTF-8 console or place as text in a UTF-8 web page. I think your PEP gives me a string that will not encode to valid UTF-8 that the outside of python world likes. Did I get this point wrong? You are right. However, if your only requirement is that it should be printable, then this is fairly underspecified. One way to get a printable string would be this function def printablestring(unprintable): return ""

Ha ha! Indeed this works, but I would have to try to turn enough of the string into a reasonable hint at the name of the file so the user can some chance of know what is being reported.

This will always return a printable version of the input string... In our application we are running fedora with the assumption that the filenames are UTF-8. When Windows systems FTP files to our system the files are in CP-1251(?) and not valid UTF-8. That would be a bug in your FTP server, no? If you want all file names to be UTF-8, then your FTP server should arrange for that.

Not a bug its the lack of a feature. We use ProFTPd that has just
implemented what is required. I forget the exact details - they are at work - when
the ftp client asks for the FEAT of the ftp server the server can say use UTF-8.
Supporting that in the server was apparently none-trivia.

Having an algorithm that says if its a string no problem, if its a byte deal with the exceptions seems simple. How do I do this detection with the PEP proposal? Do I end up using the byte interface and doing the utf-8 decode myself? No, you should encode using the "strict" error handler, with the locale encoding. If the file name encodes successfully, it's correct, otherwise, it's broken.

O.k. I understand.

Barry

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