Re: os.path.normcase rationale?
Chris Withers writes: > On 21/09/2010 01:02, Steven D'Aprano wrote: > > What do you mean "the filesystem"? > > > > If I look at the available devices on my system now, I see: > > > > 2 x FAT-32 filesystems > > 1 x ext2 filesystem > > 3 x ext3 filesystems > > 1 x NTFS filesystem > > 1 x UDF filesystem > > Right, and each of these will know what it thinks a file's "real" name > is, along with potentially accepting as set of synonyms for them... They will know internally, but Python has no way of asking them AFAICT, short of creating a file on the filesystem. That's far outside the bailiwick of the function in question. > > Which one is "the" filesystem? > > Whichever one you're getting the file from... Who said anything about “getting the file”? The parameter to the function is a path, which need not already exist, and which need not refer to *any* extant filesystem. > > If you are suggesting that os.path.normcase(filename) should > > determine which filesystem actually applies to filename at runtime, > > and hence work out what rules apply, what do you suggest should > > happen if the given path doesn't actually exist? > > I'd suggest an exception be raised. You really must have an entirely different function in mind. I suggest you look for it by another name, because ‘os.path.normcase’ already does something entirely different. > I didn't say it was an easy problem, but the current normpath is a > waste of space... This seems to be code for “it doesn't do what I expected, and now I don't want to use it”. Surely the solution is clear: don't use it. -- \“The industrial system is profoundly dependent on commercial | `\ television and could not exist in its present form without it.” | _o__)—John Kenneth Galbraith, _The New Industrial State_, 1967 | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On 21/09/2010 01:02, Steven D'Aprano wrote: On Mon, 20 Sep 2010 19:45:37 +0100, Chris Withers wrote: Well, no, that doesn't feel right. Normalisation of case, for me, means "give me the case as the filesystem thinks it should be", What do you mean "the filesystem"? If I look at the available devices on my system now, I see: 2 x FAT-32 filesystems 1 x ext2 filesystem 3 x ext3 filesystems 1 x NTFS filesystem 1 x UDF filesystem Right, and each of these will know what it thinks a file's "real" name is, along with potentially accepting as set of synonyms for them... and if I ever get my act together to install Basilisk II, as I've been threatening to do for the last five years, there will also be at least one 1 x HFS filesystem. Which one is "the" filesystem? Whichever one you're getting the file from... If you are suggesting that os.path.normcase(filename) should determine which filesystem actually applies to filename at runtime, and hence work out what rules apply, what do you suggest should happen if the given path doesn't actually exist? I'd suggest an exception be raised. Really, what's the point of normcase if it's basically just "if os=='win': return path.lower()" What if it's a filesystem that the normpath developers haven't seen or considered before? I didn't say it was an easy problem, but the current normpath is a waste of space... Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On Tue, 21 Sep 2010 10:12:27 +1000, Ben Finney wrote: > Another is that filesystems don't have a standard way of determining > whether they are case-sensitive. The operating system's driver for that > particular filesystem knows, I'm not even sure that's true; with a networked filesytem, some parts of it may be case-sensitive and others case-insensitve (e.g. if you export a Linux filesystem which includes Windows filesystems mounted beneath the root of the export). -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
Steven D'Aprano wrote: On Mon, 20 Sep 2010 19:45:37 +0100, Chris Withers wrote: Well, no, that doesn't feel right. Normalisation of case, for me, means "give me the case as the filesystem thinks it should be", What do you mean "the filesystem"? Well, if it were me, it would be either the filesystem in the path that's being norm'ed, or if no path is explicity stated, the filesystem that is hosting the current directory. If I look at the available devices on my system now, I see: 2 x FAT-32 filesystems 1 x ext2 filesystem 3 x ext3 filesystems 1 x NTFS filesystem 1 x UDF filesystem and if I ever get my act together to install Basilisk II, as I've been threatening to do for the last five years, there will also be at least one 1 x HFS filesystem. Which one is "the" filesystem? If you are suggesting that os.path.normcase(filename) should determine which filesystem actually applies to filename at runtime, and hence work out what rules apply, what do you suggest should happen if the given path doesn't actually exist? What if it's a filesystem that the normpath developers haven't seen or considered before? Something along those lines seems to be happening now. Observe what happens on my XP machine with an NTFS drive. --> import foo Traceback (most recent call last): File "", line 1, in ImportError: No module named foo --> import FOO Traceback (most recent call last): File "", line 1, in ImportError: No module named FOO --> import fOo Traceback (most recent call last): File "", line 1, in ImportError: No module named fOo --> import Foo Foo has been imported! ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
Chris Withers writes: > What I expected it to mean was "give me what the filesystem thinks > this file path is", which doesn't seem unreasonable and would be a lot > more useful, no matter the platform... Two problems with that. One is that the entry specified by the path may not exist on the filesystem, but the function shouldn't care about that. It's for “normalising” a path, whether the entry referred to exists or not. Another is that filesystems don't have a standard way of determining whether they are case-sensitive. The operating system's driver for that particular filesystem knows, but Python doesn't. So in this case you'll simply have to adjust your expectations. -- \ “I prayed for twenty years but received no answer until I | `\ prayed with my legs.” —Frederick Douglass, escaped slave | _o__) | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On Mon, 20 Sep 2010 19:45:37 +0100, Chris Withers wrote: > Well, no, that doesn't feel right. Normalisation of case, for me, means > "give me the case as the filesystem thinks it should be", What do you mean "the filesystem"? If I look at the available devices on my system now, I see: 2 x FAT-32 filesystems 1 x ext2 filesystem 3 x ext3 filesystems 1 x NTFS filesystem 1 x UDF filesystem and if I ever get my act together to install Basilisk II, as I've been threatening to do for the last five years, there will also be at least one 1 x HFS filesystem. Which one is "the" filesystem? If you are suggesting that os.path.normcase(filename) should determine which filesystem actually applies to filename at runtime, and hence work out what rules apply, what do you suggest should happen if the given path doesn't actually exist? What if it's a filesystem that the normpath developers haven't seen or considered before? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On 17/09/2010 03:35, Nobody wrote: os.path.normcase(path) Normalize the case of a pathname. On Unix and Mac OS X, this returns the path unchanged; on case-insensitive filesystems, it converts the path to lowercase. On Windows, it also converts forward slashes to backward slashes. It implies that the behaviour depends upon the actual filesystem, which isn't the case. It only depends upon the platform, i.e. it assumes that all filenames are case-sensitive on Unix systems and case-insensitive on Windows. But Unix systems can access FAT/SMBFS/etc filesystems which are case-insensitive. Right, so in its current form it seems pretty useless ;-) What I expected it to mean was "give me what the filesystem thinks this file path is", which doesn't seem unreasonable and would be a lot more useful, no matter the platform... Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On 16/09/2010 00:14, Gregory Ewing wrote: Ben Finney wrote: it doesn't matter what the case is, so there's no need for anything more complex than all lowercase. Also doing what was suggested would require looking at what's in the file system, which would be a lot of bother to go to for no good reason, and would fail for paths that don't correspond to an existing file. .lower() is shorter to type, if that's what you want... Chris -- Simplistix - Content Management, Batch Processing & Python Consulting - http://www.simplistix.co.uk -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On 15/09/2010 22:12, Ben Finney wrote:
Chris Withers writes:
I'm curious as to why, with a file called "Foo.txt"
os.path.normcase('FoO.txt') will return "foo.txt" rather than
"Foo.txt"?
What kind of answer are you looking for?
A direct answer would be: it does that because on case-insensitive
filesystems, it doesn't matter what the case is, so there's no need for
anything more complex than all lowercase.
Well, no, that doesn't feel right. Normalisation of case, for me, means
"give me the case as the filesystem thinks it should be", not "just
lowercase it all". This makes a difference; I hit it by way of version
pinning in buildout, the culprit being setuptools calling normcase on
distributions found on the filesystem on Windows. Buildout's version
pinning is case sensitive (arguably a bug) and so doesn't work when
setuptools's use of normcase ends up with he distribution name being
lowercased, even though the case is correct on the file system...
Yes, I know the behaviour is documented
The docstring is fairly poor, IMO. You might want to submit a bug report
to improve it.
I think it would have been a lot more confusing had it not been
mentioned that it was just lowercasing everything...
Chris
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Re: os.path.normcase rationale?
On Thu, 16 Sep 2010 07:12:16 +1000, Ben Finney wrote: >> Yes, I know the behaviour is documented > > The docstring is fairly poor, IMO. You might want to submit a bug report > to improve it. The description in the library documentation is misleading: os.path.normcase(path) Normalize the case of a pathname. On Unix and Mac OS X, this returns the path unchanged; on case-insensitive filesystems, it converts the path to lowercase. On Windows, it also converts forward slashes to backward slashes. It implies that the behaviour depends upon the actual filesystem, which isn't the case. It only depends upon the platform, i.e. it assumes that all filenames are case-sensitive on Unix systems and case-insensitive on Windows. But Unix systems can access FAT/SMBFS/etc filesystems which are case-insensitive. -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
On Wed, 15 Sep 2010 14:49:09 +0100, Chris Withers wrote:
> I'm curious as to why, with a file called "Foo.txt"
> os.path.normcase('FoO.txt') will return "foo.txt" rather than "Foo.txt"?
normcase() doesn't look at the filesystem; it's just string manipulation.
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Re: os.path.normcase rationale?
Ben Finney wrote: it doesn't matter what the case is, so there's no need for anything more complex than all lowercase. Also doing what was suggested would require looking at what's in the file system, which would be a lot of bother to go to for no good reason, and would fail for paths that don't correspond to an existing file. -- Greg -- http://mail.python.org/mailman/listinfo/python-list
Re: os.path.normcase rationale?
Chris Withers writes:
> I'm curious as to why, with a file called "Foo.txt"
> os.path.normcase('FoO.txt') will return "foo.txt" rather than
> "Foo.txt"?
What kind of answer are you looking for?
A direct answer would be: it does that because on case-insensitive
filesystems, it doesn't matter what the case is, so there's no need for
anything more complex than all lowercase.
> Yes, I know the behaviour is documented
The docstring is fairly poor, IMO. You might want to submit a bug report
to improve it.
> but I'm wondering if anyone can remember the rationale for that
> behaviour?
I can't speak to that. Does the above answer seem sufficient?
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os.path.normcase rationale?
Hi All,
I'm curious as to why, with a file called "Foo.txt"
os.path.normcase('FoO.txt') will return "foo.txt" rather than "Foo.txt"?
Yes, I know the behaviour is documented, but I'm wondering if anyone can
remember the rationale for that behaviour?
cheers,
Chris
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