Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #10470 > unrolled thread

list comprehension to do os.path.split_all ?

Back to article view | Back to comp.lang.python

Contents

  list comprehension to do os.path.split_all ? gry <georgeryoung@gmail.com> - 2011-07-28 13:18 -0700
    Re: list comprehension to do os.path.split_all ? Stefaan Himpe <stefaan.himpe@gmail.com> - 2011-07-28 22:32 +0200
    Re: list comprehension to do os.path.split_all ? Neil Cerutti <neilc@norwich.edu> - 2011-07-28 20:36 +0000
      Re: list comprehension to do os.path.split_all ? Ethan Furman <ethan@stoneleaf.us> - 2011-07-28 14:03 -0700
    Re: list comprehension to do os.path.split_all ? Alan Meyer <ameyer2@yahoo.com> - 2011-07-28 16:40 -0400
      Re: list comprehension to do os.path.split_all ? TheSaint <no@nowhere.net.no> - 2011-07-29 22:29 +0800
    Re: list comprehension to do os.path.split_all ? Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-28 14:44 -0600
    Re: list comprehension to do os.path.split_all ? Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-28 14:47 -0600
    Re: list comprehension to do os.path.split_all ? Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-28 15:04 -0600
    Re: list comprehension to do os.path.split_all ? Alexander Kapps <alex.kapps@web.de> - 2011-07-28 23:06 +0200
    Re: list comprehension to do os.path.split_all ? Emile van Sebille <emile@fenx.com> - 2011-07-28 14:15 -0700
    Re: list comprehension to do os.path.split_all ? Ian Kelly <ian.g.kelly@gmail.com> - 2011-07-28 15:31 -0600
      Re: list comprehension to do os.path.split_all ? Carl Banks <pavlovevidence@gmail.com> - 2011-07-29 12:30 -0700
        Re: list comprehension to do os.path.split_all ? Alexander Kapps <alex.kapps@web.de> - 2011-07-29 22:22 +0200
        Re: list comprehension to do os.path.split_all ? Michael Poeltl <michael.poeltl@univie.ac.at> - 2011-07-30 02:23 +0200
        Re: list comprehension to do os.path.split_all ? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-30 10:55 +1000
        Re: list comprehension to do os.path.split_all ? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-07-29 22:17 -0700
        Re: list comprehension to do os.path.split_all ? Michael Poeltl <michael.poeltl@univie.ac.at> - 2011-07-31 07:40 +0200
    Re: list comprehension to do os.path.split_all ? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2011-07-28 21:15 -0700
      Re: list comprehension to do os.path.split_all ? Neil Cerutti <neilc@norwich.edu> - 2011-07-29 12:40 +0000
        Re: list comprehension to do os.path.split_all ? Hrvoje Niksic <hniksic@xemacs.org> - 2011-07-31 08:42 +0200

Page 1 of 2  [1] 2  Next page →

#10470 — list comprehension to do os.path.split_all ?

[python 2.7] I have a (linux) pathname that I'd like to split
completely into a list of components, e.g.:
   '/home/gyoung/hacks/pathhack/foo.py'  -->  ['home', 'gyoung',
'hacks', 'pathhack', 'foo.py']

os.path.split gives me a tuple of dirname,basename, but there's no
os.path.split_all function.

I expect I can do this with some simple loop, but I have such faith in
the wonderfulness of list comprehensions, that it seems like there
should be a way to use them for an elegant solution of my problem.
I can't quite work it out.  Any brilliant ideas?   (or other elegant
solutions to the problem?)

-- George

[toc] | [next] | [standalone]

#10471

Hi,

> [python 2.7] I have a (linux) pathname that I'd like to split
> completely into a list of components, e.g.:
>     '/home/gyoung/hacks/pathhack/foo.py'  -->   ['home', 'gyoung',
> 'hacks', 'pathhack', 'foo.py']

Not sure what your exact requirements are, but the following seems to work:

pathname = '/home/gyoung/hacks/pathhack/foo.py'
print pathname[1:].split("/")

Note that this would only work for absolute linux paths (i.e. starting 
with "/").

Best regards,
Stefaan.

[toc] | [prev] | [next] | [standalone]

#10472

On 2011-07-28, gry <georgeryoung@gmail.com> wrote:
> [python 2.7] I have a (linux) pathname that I'd like to split
> completely into a list of components, e.g.:
>    '/home/gyoung/hacks/pathhack/foo.py'  -->  ['home', 'gyoung',
> 'hacks', 'pathhack', 'foo.py']
>
> os.path.split gives me a tuple of dirname,basename, but there's
> no os.path.split_all function.
>
> I expect I can do this with some simple loop, but I have such
> faith in the wonderfulness of list comprehensions, that it
> seems like there should be a way to use them for an elegant
> solution of my problem. I can't quite work it out.  Any
> brilliant ideas?   (or other elegant solutions to the problem?)

If an elegant solution doesn't occur to me right away, then I
first compose the most obvious solution I can think of. Finally,
I refactor it until elegance is either achieved or imagined.

-- 
Neil Cerutti

[toc] | [prev] | [next] | [standalone]

#10477

Neil Cerutti wrote:
> If an elegant solution doesn't occur to me right away, then I
> first compose the most obvious solution I can think of. Finally,
> I refactor it until elegance is either achieved or imagined.

+1 QOTW

[toc] | [prev] | [next] | [standalone]

#10473

On 7/28/2011 4:18 PM, gry wrote:
> [python 2.7] I have a (linux) pathname that I'd like to split
> completely into a list of components, e.g.:
>     '/home/gyoung/hacks/pathhack/foo.py'  -->   ['home', 'gyoung',
> 'hacks', 'pathhack', 'foo.py']
>
> os.path.split gives me a tuple of dirname,basename, but there's no
> os.path.split_all function.
>
> I expect I can do this with some simple loop, but I have such faith in
> the wonderfulness of list comprehensions, that it seems like there
> should be a way to use them for an elegant solution of my problem.
> I can't quite work it out.  Any brilliant ideas?   (or other elegant
> solutions to the problem?)
>
> -- George

This is not properly portable to all OS, but you could simply split on 
the slash character, e.g.,

     pathname.split('/')

   Alan

[toc] | [prev] | [next] | [standalone]

#10516

Alan Meyer wrote:

> This is not properly portable to all OS, but you could simply split on
> the slash character, e.g.,
> 
> pathname.split('/')

more portable  pathname.split(os.sep)

[toc] | [prev] | [next] | [standalone]

#10474

On Thu, Jul 28, 2011 at 2:18 PM, gry <georgeryoung@gmail.com> wrote:
> [python 2.7] I have a (linux) pathname that I'd like to split
> completely into a list of components, e.g.:
>   '/home/gyoung/hacks/pathhack/foo.py'  -->  ['home', 'gyoung',
> 'hacks', 'pathhack', 'foo.py']
>
> os.path.split gives me a tuple of dirname,basename, but there's no
> os.path.split_all function.
>
> I expect I can do this with some simple loop, but I have such faith in
> the wonderfulness of list comprehensions, that it seems like there
> should be a way to use them for an elegant solution of my problem.
> I can't quite work it out.  Any brilliant ideas?   (or other elegant
> solutions to the problem?)

path = '/home/gyoung/hacks/pathhack/foo.py'
parts = [part for path, part in iter(lambda: os.path.split(path), ('/', ''))]
parts.reverse()
print parts

But that's horrendously ugly.  Just write a generator with a while
loop or something.

[toc] | [prev] | [next] | [standalone]

#10476

On Thu, Jul 28, 2011 at 2:44 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> path = '/home/gyoung/hacks/pathhack/foo.py'
> parts = [part for path, part in iter(lambda: os.path.split(path), ('/', ''))]
> parts.reverse()
> print parts
>
> But that's horrendously ugly.  Just write a generator with a while
> loop or something.

Also, note that if the path does not start with '/', the result will
be an infinite loop.

[toc] | [prev] | [next] | [standalone]

#10478

On Thu, Jul 28, 2011 at 2:47 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
> On Thu, Jul 28, 2011 at 2:44 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>> path = '/home/gyoung/hacks/pathhack/foo.py'
>> parts = [part for path, part in iter(lambda: os.path.split(path), ('/', ''))]
>> parts.reverse()
>> print parts
>>
>> But that's horrendously ugly.  Just write a generator with a while
>> loop or something.
>
> Also, note that if the path does not start with '/', the result will
> be an infinite loop.

Oh, and this won't work at all in Python 3, because it relies on the
lambda having access to the list comprehension scope.

[toc] | [prev] | [next] | [standalone]

#10479

On 28.07.2011 22:44, Ian Kelly wrote:
> On Thu, Jul 28, 2011 at 2:18 PM, gry<georgeryoung@gmail.com>  wrote:
>> [python 2.7] I have a (linux) pathname that I'd like to split
>> completely into a list of components, e.g.:
>>    '/home/gyoung/hacks/pathhack/foo.py'  -->    ['home', 'gyoung',
>> 'hacks', 'pathhack', 'foo.py']
>>
>> os.path.split gives me a tuple of dirname,basename, but there's no
>> os.path.split_all function.
>>
>> I expect I can do this with some simple loop, but I have such faith in
>> the wonderfulness of list comprehensions, that it seems like there
>> should be a way to use them for an elegant solution of my problem.
>> I can't quite work it out.  Any brilliant ideas?   (or other elegant
>> solutions to the problem?)
>
> path = '/home/gyoung/hacks/pathhack/foo.py'
> parts = [part for path, part in iter(lambda: os.path.split(path), ('/', ''))]
> parts.reverse()
> print parts
>
> But that's horrendously ugly.  Just write a generator with a while
> loop or something.


pathname = '/home/gyoung/hacks/pathhack/foo.py'
parts = [part for part in pathname.split(os.path.sep) if part]
print parts

['home', 'gyoung', 'hacks', 'pathhack', 'foo.py']

[toc] | [prev] | [next] | [standalone]

#10481

On 7/28/2011 1:18 PM gry said...
> [python 2.7] I have a (linux) pathname that I'd like to split
> completely into a list of components, e.g.:
>     '/home/gyoung/hacks/pathhack/foo.py'  -->   ['home', 'gyoung',
> 'hacks', 'pathhack', 'foo.py']
>
> os.path.split gives me a tuple of dirname,basename, but there's no
> os.path.split_all function.
>

Why not just split?

'/home/gyoung/hacks/pathhack/foo.py'.split(os.sep)

Emile

[toc] | [prev] | [next] | [standalone]

#10483

On Thu, Jul 28, 2011 at 3:15 PM, Emile van Sebille <emile@fenx.com> wrote:
> On 7/28/2011 1:18 PM gry said...
>>
>> [python 2.7] I have a (linux) pathname that I'd like to split
>> completely into a list of components, e.g.:
>>    '/home/gyoung/hacks/pathhack/foo.py'  -->   ['home', 'gyoung',
>> 'hacks', 'pathhack', 'foo.py']
>>
>> os.path.split gives me a tuple of dirname,basename, but there's no
>> os.path.split_all function.
>>
>
> Why not just split?
>
> '/home/gyoung/hacks/pathhack/foo.py'.split(os.sep)

Using os.sep doesn't make it cross-platform. On Windows:

>>> os.path.split(r'C:\windows')
('C:\\', 'windows')
>>> os.path.split(r'C:/windows')
('C:/', 'windows')
>>> r'C:\windows'.split(os.sep)
['C:', 'windows']
>>> r'C:/windows'.split(os.sep)
['C:/windows']

[toc] | [prev] | [next] | [standalone]

#10534

On Thursday, July 28, 2011 2:31:43 PM UTC-7, Ian wrote:
> On Thu, Jul 28, 2011 at 3:15 PM, Emile van Sebille <em...@fenx.com> wrote:
> > On 7/28/2011 1:18 PM gry said...
> >>
> >> [python 2.7] I have a (linux) pathname that I'd like to split
> >> completely into a list of components, e.g.:
> >>    '/home/gyoung/hacks/pathhack/foo.py'  -->   ['home', 'gyoung',
> >> 'hacks', 'pathhack', 'foo.py']
> >>
> >> os.path.split gives me a tuple of dirname,basename, but there's no
> >> os.path.split_all function.
> >>
> >
> > Why not just split?
> >
> > '/home/gyoung/hacks/pathhack/foo.py'.split(os.sep)
> 
> Using os.sep doesn't make it cross-platform. On Windows:
> 
> >>> os.path.split(r'C:\windows')
> ('C:\\', 'windows')
> >>> os.path.split(r'C:/windows')
> ('C:/', 'windows')
> >>> r'C:\windows'.split(os.sep)
> ['C:', 'windows']
> >>> r'C:/windows'.split(os.sep)
> ['C:/windows']

It's not even fullproof on Unix.

'/home//h1122/bin///ghi/'.split('/')

['','home','','bin','','','ghi','']

The whole point of the os.path functions are to take care of whatever oddities there are in the path system.  When you use string manipulation to manipulate paths, you bypass all of that and leave yourself open to those oddities, and then you find your applications break when a user enters a doubled slash.

So stick to os.path.


Carl Banks

[toc] | [prev] | [next] | [standalone]

#10541

On 29.07.2011 21:30, Carl Banks wrote:

> It's not even fullproof on Unix.
>
> '/home//h1122/bin///ghi/'.split('/')
>
> ['','home','','bin','','','ghi','']
>
> The whole point of the os.path functions are to take care of whatever oddities there are in the path system.  When you use string manipulation to manipulate paths, you bypass all of that and leave yourself open to those oddities, and then you find your applications break when a user enters a doubled slash.
>
> So stick to os.path.
>
>
> Carl Banks

This would also be fixed with normpath() as Dennis Lee Bieber 
suggested. And my solution with list comprehensions handles this too.

Still, there might be other path oddities which would break here. I 
think, that something like a split_all() function should be 
available in the stdlib, no?

Actually, it isn't the first time, where I wonder why 
os.path.split() doesn't do this already. I mean, str.split() doesn't 
only split on the first part, right?

[toc] | [prev] | [next] | [standalone]

#10557

* Alexander Kapps <alex.kapps@web.de> [2011-07-29 22:30]:
> On 29.07.2011 21:30, Carl Banks wrote:
>
>> It's not even fullproof on Unix.
>>
>> '/home//h1122/bin///ghi/'.split('/')
>>
>> ['','home','','bin','','','ghi','']
what about this?                                                                
>>> ' '.join('/home//h1122/bin///ghi/'.split('/')).split()                      
['home', 'h1122', 'bin', 'ghi']                                                 
>>>                                                                             
;-)                                                                             
regards                                                                         
Michael

>> Carl Banks
>
> This would also be fixed with normpath() as Dennis Lee Bieber suggested. 
> And my solution with list comprehensions handles this too.
>
> Still, there might be other path oddities which would break here. I  
> think, that something like a split_all() function should be available in 
> the stdlib, no?
>
> Actually, it isn't the first time, where I wonder why os.path.split() 
> doesn't do this already. I mean, str.split() doesn't only split on the 
> first part, right?
> -- 
> http://mail.python.org/mailman/listinfo/python-list
>

-- 
Michael Poeltl
Computational Materials Physics      voice: +43-1-4277-51409
Univ. Wien, Sensengasse 8/12         fax:   +43-1-4277-9514 (or 9513) 
A-1090 Wien, AUSTRIA   cmp.mpi.univie.ac.at 

[toc] | [prev] | [next] | [standalone]

#10560

Carl Banks wrote:

> It's not even fullproof on Unix.
> 
> '/home//h1122/bin///ghi/'.split('/')
> 
> ['','home','','bin','','','ghi','']


What? No. Absolutely not -- that would be a major bug. Did you actually try
it?

>>> '/home//h1122/bin///ghi/'.split('/')
['', 'home', '', 'h1122', 'bin', '', '', 'ghi', '']

Exactly as expected, and correct.

Now obviously if you intend treating this as a list of path components, you
have to filter out the empty strings, but otherwise works fine.



-- 
Steven

[toc] | [prev] | [next] | [standalone]

#10572

On Fri, 29 Jul 2011 22:22:54 +0200, Alexander Kapps <alex.kapps@web.de>
declaimed the following in gmane.comp.python.general:


> Actually, it isn't the first time, where I wonder why 
> os.path.split() doesn't do this already. I mean, str.split() doesn't 
> only split on the first part, right?

	But there is a conceptual difference... The last element of a path
is a file (or directory name) contained within the preceding path name
portion.

	But a string has no context...
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

[toc] | [prev] | [next] | [standalone]

#10615

* Michael Torrie <torriem@gmail.com> [2011-07-31 03:44]:
> On Jul 29, 2011 6:33 PM, "Michael Poeltl" <michael.poeltl@univie.ac.at>
> wrote:
> >
> > what about this?
> > >>> ' '.join('/home//h1122/bin///ghi/'.split('/')).split()
> > ['home', 'h1122', 'bin', 'ghi']
> > >>>
> 
> Doesn't work on filenames with spaces in them.
you are right; me, I never put spaces into my filenames and so I didn't
think of this possibility.

so there is another idea, which will not work on dirnames 'with spacs in
them' ;-)
>>> p = '/path//to///file/i am a file'
>>> ' '.join(os.path.split(p)[0].split('/')).split().__add__([os.path.split(p)[1]])
['path', 'to', 'file', 'i am a file']
>>>
-- 
Michael Poeltl
Computational Materials Physics      voice: +43-1-4277-51409
Univ. Wien, Sensengasse 8/12         fax:   +43-1-4277-9514 (or 9513) 
A-1090 Wien, AUSTRIA   cmp.mpi.univie.ac.at 
-----------------------------------------------------------------
slackware-12.2/ubuntu-10.10 | vim-7.3 | python-3.2.1 | mutt-1.5.18 | elinks-0.12

[toc] | [prev] | [next] | [standalone]

#10498

On Thu, 28 Jul 2011 15:31:43 -0600, Ian Kelly <ian.g.kelly@gmail.com>
declaimed the following in gmane.comp.python.general:

> Using os.sep doesn't make it cross-platform. On Windows:
> 
> >>> os.path.split(r'C:\windows')
> ('C:\\', 'windows')
> >>> os.path.split(r'C:/windows')
> ('C:/', 'windows')
> >>> r'C:\windows'.split(os.sep)
> ['C:', 'windows']
> >>> r'C:/windows'.split(os.sep)
> ['C:/windows']

	Fine... So normpath it first...

>>> os.path.normpath(r'C:/windows').split(os.sep)
['C:', 'windows']
>>> 
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

[toc] | [prev] | [next] | [standalone]

#10512

On 2011-07-29, Dennis Lee Bieber <wlfraed@ix.netcom.com> wrote:
> On Thu, 28 Jul 2011 15:31:43 -0600, Ian Kelly
> <ian.g.kelly@gmail.com> declaimed the following in
> gmane.comp.python.general:
>
>> Using os.sep doesn't make it cross-platform. On Windows:
>> 
>> >>> os.path.split(r'C:\windows')
>> ('C:\\', 'windows')
>> >>> os.path.split(r'C:/windows')
>> ('C:/', 'windows')
>> >>> r'C:\windows'.split(os.sep)
>> ['C:', 'windows']
>> >>> r'C:/windows'.split(os.sep)
>> ['C:/windows']
>
> 	Fine... So normpath it first...
>
>>>> os.path.normpath(r'C:/windows').split(os.sep)
> ['C:', 'windows']
>>>> 

Here's a solution adapted from an initially recursive attempt.
The tests are currently somewhat gnarled to avoid displaying
os.path.sep. A simpler solution probably reimplement os.path.split,
an inconvenient implementation detail.

import os

def split_path(path):
    """Split path into a series of directory names, and return it
    as a list.

    If path is absolute, the first element in the list will be be
    os.path.sep.

    >>> p = split_path('/smith/jones')
    >>> p[0] == os.path.sep
    True
    >>> p[1:]
    ['smith', 'jones']

    >>> split_path('smith/jones')
    ['smith', 'jones']

    >>> split_path('')
    []

    >>> p = split_path('/')
    >>> p[0] == os.path.sep
    True
    >>> len(p)
    1
    """
    head, tail = os.path.split(path)
    retval = []
    while tail != '':
        retval.append(tail)
        head, tail = os.path.split(head)
    else:
        if os.path.isabs(path):
            retval.append(os.path.sep)
        return list(reversed(retval))

if __name__ == '__main__':
    import doctest
    doctest.testmod()

-- 
Neil Cerutti

[toc] | [prev] | [next] | [standalone]

Page 1 of 2  [1] 2  Next page →

Back to top | Article view | comp.lang.python

csiph-web