[Python-Dev] urllib.urlretrieve() and handling 550 errors when reading from FTP (original) (raw)

Brett C. bac at OCF.Berkeley.EDU
Sun Jul 11 04:04:12 CEST 2004

Guido van Rossum wrote:

Bug #635453 reports that when you use urllib.urlretrieve() to read from an FTP server and the file you are trying to get does not have the proper permissions for you, you are given a listing of the directory instead of an exception (this is all done by Lib/urllib.py:752).

Now this doesn't make sense to me and I suspect most people would agree. But having that explicit line there on top of it having been in the file since it was renamed from urlopen way backin 1994 makes me hesitate before I delete the line. Anyone have issues if I ditch the line so an exception is raised instead of getting a directory listing instead? If you remove this, you won't be able to get a directory listing of directories. I tried this with and without the line; with that line in, it gives a directlry listing, without it gives an IOError (Not a regular file):

urllib.urlretrieve("ftp://ftp.python.org/pub", "xyzzy") So I'd be against deleting this, unless there's a different way to get directory listings.

Try it again but with a trailing slash on the address. With the line removed it will fetch the directory. Otherwise it errors out. The code apparently tries to get the file and when it fails with a 550 (meaning the file cannot be accessed because of permissions or lack of existence), the code then send a LIST command which lists whatever the argument is, file or directory.

Unfortunately I can't think of a good way to detect the difference between a file and a directory that just doesn't have the ending slash beyond reading the output and seeing if it is a single listing for a file with the same name as the LIST request.

-Brett

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