[Python-Dev] The path module PEP

[Ian Bicking]

Jason Orendorff wrote:
>>    [...]omitted:
>>    * Function for opening a path - better handled by the builtin
>>      open().
> 
> 
> Aside:  I added this to support a few people who liked the idea of
> "openable objects", meaning anything that has .open(), analogous to
> "writeable objects" being anything with .write().  I don't use it
> personally.

Losing .open() would make it much harder for anyone wanting to write, 
say, a URI library that implements the Path API.

> I suspect you'll be asked to change the PEP to remove __div__ for
> starters, in which case I propose using the Path constructor as the
> replacement for os.path.join().  In that case, Path.joinpath can be
> dropped.

I'm -1 on this too.  This means people will be hardcoding the specific 
class they expect, so you can't pass in other classes.  E.g., this will 
fail:

   def read_config(home_dir):
       f = open(Path(home_dir, '.config_file'))
       c = f.read()
       f.close()
       return c

   read_config(URI('http://localhost/foo'))

I'm personally +1 on /.  I think people who think it is confusing are 
giving a knee-jerk reaction.  It's very easy to tell the difference 
between file-related code and math-related code, and / is currently only 
used for math.  In contrast, + is used for concatenation and addition, 
and these are far more ambiguous from context -- but still it doesn't 
cause that many problems.  But barring /, .joinpath() should remain. 
Too bad there isn't a shorter name, except .join() which is taken.

I would also, though, note that there are some security issues.  When 
you use open() or other path-related functions, you *know* you are doing 
filesystem operations.  You can't be getting some weird object that does 
who-knows-what.  For the most part if you can get an arbitrary object 
into the system then the system is just broken, but I can imagine cases 
where this encourages people to do bad things.  I only bring this up 
because it reminds me of PHP allowed over-the-net includes, which always 
seemed like a bad idea.

-- 
Ian Bicking  /  ianb at colorstudy.com  /  http://blog.ianbicking.org