[Python-Dev] The path module PEP

[Bob Ippolito]

On Jan 25, 2006, at 3:42 PM, Tony Meyer wrote:

> [Ian Bicking]
>> If it were possible to use .join() for joining paths, I think I
>> wouldn't mind so much.  But reusing a string method for something
>> very different seems like a bad idea.  So we're left with .joinpath
>> ().  Still better than os.path.join() I guess, but only a little.
>> I guess that's why I'm +1 on /.
>
> Why does reusing a string method for something very different seem
> like a bad idea, but reusing a mathematical operator for something
> very different seem like a good idea?  Path's aren't strings, so join
> () seems the logical choice.  (There are also alternatives to
> "joinpath" if the name is the thing: add(), for example).

join() is already defined for strings, division is not.  Different  
namespace... just like + is concatenation for list+list, tuple+tuple,  
basestring+basestring, but it's addition for numbers...

>>>   * Not every platform that Python supports has '/' as the path
>>> separator.  Windows, a pretty major one, has '\'.  I have no idea
>>> what various portable devices use, but there's a reasonable
>>> chance  it's not '/'.
>>
>> I believe all platforms support /; at least Windows and Mac do, in
>> addition to their native separators.
>
> This is not strictly true.  Using '/' can lead to strange results
> with Windows, where it gets interpreted as a flag instead.  It's not
> reliable, it's not the path separator that Windows users/developers
> understand, and it's not the correct (i.e. according to Microsoft)
> path separator.  If by Mac you mean OS X, then that's just another
> *nix based OS.  I'm pretty sure that pre OS X (which isn't supported
> any more anyway, right?) '/' was not, in fact, supported, and that
> ":" was required.  I also believe it's important to remember that
> Windows and *nix descendants are not "all platforms".

Mac OS X understands '/' as the separator at the POSIX layer, but ':'  
as the path separator at the Carbon API (which is only used in  
obscure places from Python).  Earlier versions of Mac OS are no  
longer supported, and you're right -- they only understood ':' as a  
path separator.

>> If anything, a good shortcut for .joinpath() will at least
>> encourage people to use it, thus discouraging hardcoding of path
>> separators.  I expect it would encourage portable paths.
>
> I'm not sure that I believe that the reason that people don't type
> "os.path.join('a', 'b')" is because they are too lazy to type it.
> However, I don't have any evidence either way, so it could be true.

In many cases, when I know I only care about *nix, I will use 'a/b'  
instead of os.path.join because it's just so much more concise and  
more obvious.

The only times I use os.path.join are when I don't know if there will  
be a trailing slash or not, or if I'm actively trying to make  
something cross-platform.

-bob