Python os path separator

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The output from all the example programs from PyMOTW has been generated with Python 2.7.8, unless otherwise noted. Some of the features described here may not be available in earlier versions of Python.

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os.path – Platform-independent manipulation of file names.¶

Writing code to work with files on multiple platforms is easy using the functions included in the os.path module. Even programs not intended to be ported between platforms should use os.path for reliable filename parsing.

Parsing Paths¶

The first set of functions in os.path can be used to parse strings representing filenames into their component parts. It is important to realize that these functions do not depend on the paths actually existing; they operate solely on the strings.

Path parsing depends on a few variable defined in os :

• os.sep — The separator between portions of the path (e.g., “ / ” or “ \ ”).
• os.extsep — The separator between a filename and the file “extension” (e.g., “ . ”).
• os.pardir — The path component that means traverse the directory tree up one level (e.g., “ .. ”).
• os.curdir — The path component that refers to the current directory (e.g., “ . ”).

split() breaks the path into 2 separate parts and returns the tuple. The second element is the last component of the path, and the first element is everything that comes before it.

import os.path for path in [ '/one/two/three', '/one/two/three/', '/', '.', '']: print '"%s" : "%s"' % (path, os.path.split(path)) 

$ python ospath_split.py "/one/two/three" : "('/one/two', 'three')" "/one/two/three/" : "('/one/two/three', '')" "/" : "('/', '')" "." : "('', '.')" "" : "('', '')"

basename() returns a value equivalent to the second part of the split() value.

import os.path for path in [ '/one/two/three', '/one/two/three/', '/', '.', '']: print '"%s" : "%s"' % (path, os.path.basename(path)) 

$ python ospath_basename.py "/one/two/three" : "three" "/one/two/three/" : "" "/" : "" "." : "." "" : ""

dirname() returns the first part of the split path:

import os.path for path in [ '/one/two/three', '/one/two/three/', '/', '.', '']: print '"%s" : "%s"' % (path, os.path.dirname(path)) 

$ python ospath_dirname.py "/one/two/three" : "/one/two" "/one/two/three/" : "/one/two/three" "/" : "/" "." : "" "" : ""

splitext() works like split() but divides the path on the extension separator, rather than the directory separator.

import os.path for path in [ 'filename.txt', 'filename', '/path/to/filename.txt', '/', '' ]: print '"%s" :' % path, os.path.splitext(path) 

$ python ospath_splitext.py "filename.txt" : ('filename', '.txt') "filename" : ('filename', '') "/path/to/filename.txt" : ('/path/to/filename', '.txt') "/" : ('/', '') "" : ('', '')

commonprefix() takes a list of paths as an argument and returns a single string that represents a common prefix present in all of the paths. The value may represent a path that does not actually exist, and the path separator is not included in the consideration, so the prefix might not stop on a separator boundary.

import os.path paths = ['/one/two/three/four', '/one/two/threefold', '/one/two/three/', ] print paths print os.path.commonprefix(paths) 

In this example the common prefix string is /one/two/three , even though one path does not include a directory named three .

$ python ospath_commonprefix.py ['/one/two/three/four', '/one/two/threefold', '/one/two/three/'] /one/two/three

Building Paths¶

Besides taking existing paths apart, you will frequently need to build paths from other strings.

To combine several path components into a single value, use join() :

import os.path for parts in [ ('one', 'two', 'three'), ('/', 'one', 'two', 'three'), ('/one', '/two', '/three'), ]: print parts, ':', os.path.join(*parts) 

$ python ospath_join.py ('one', 'two', 'three') : one/two/three ('/', 'one', 'two', 'three') : /one/two/three ('/one', '/two', '/three') : /three

It’s also easy to work with paths that include “variable” components that can be expanded automatically. For example, expanduser() converts the tilde ( ~ ) character to a user’s home directory.

import os.path for user in [ '', 'dhellmann', 'postgres' ]: lookup = '~' + user print lookup, ':', os.path.expanduser(lookup) 

$ python ospath_expanduser.py ~ : /Users/dhellmann ~dhellmann : /Users/dhellmann ~postgres : /Library/PostgreSQL/9.0

expandvars() is more general, and expands any shell environment variables present in the path.

import os.path import os os.environ['MYVAR'] = 'VALUE' print os.path.expandvars('/path/to/$MYVAR') 

$ python ospath_expandvars.py /path/to/VALUE

Normalizing Paths¶

Paths assembled from separate strings using join() or with embedded variables might end up with extra separators or relative path components. Use normpath() to clean them up:

import os.path for path in [ 'one//two//three', 'one/./two/./three', 'one/../one/two/three', ]: print path, ':', os.path.normpath(path) 

$ python ospath_normpath.py one//two//three : one/two/three one/./two/./three : one/two/three one/../one/two/three : one/two/three

To convert a relative path to a complete absolute filename, use abspath() .

import os.path for path in [ '.', '..', './one/two/three', '../one/two/three']: print '"%s" : "%s"' % (path, os.path.abspath(path)) 

$ python ospath_abspath.py "." : "/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/ospath" ".." : "/Users/dhellmann/Documents/PyMOTW/src/PyMOTW" "./one/two/three" : "/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/ospath/one/two/three" "../one/two/three" : "/Users/dhellmann/Documents/PyMOTW/src/PyMOTW/one/two/three"

File Times¶

Besides working with paths, os.path also includes some functions for retrieving file properties, which can be more convenient than calling os.stat() :

import os.path import time print 'File :', __file__ print 'Access time :', time.ctime(os.path.getatime(__file__)) print 'Modified time:', time.ctime(os.path.getmtime(__file__)) print 'Change time :', time.ctime(os.path.getctime(__file__)) print 'Size :', os.path.getsize(__file__) 

$ python ospath_properties.py File : ospath_properties.py Access time : Thu Feb 21 06:36:29 2013 Modified time: Sat Feb 19 19:18:23 2011 Change time : Sat Jul 16 12:28:42 2011 Size : 495

Testing Files¶

When your program encounters a path name, it often needs to know whether the path refers to a file or directory. If you are working on a platform that supports it, you may need to know if the path refers to a symbolic link or mount point. You will also want to test whether the path exists or not. os.path provides functions to test all of these conditions.

import os.path for file in [ __file__, os.path.dirname(__file__), '/', './broken_link']: print 'File :', file print 'Absolute :', os.path.isabs(file) print 'Is File? :', os.path.isfile(file) print 'Is Dir? :', os.path.isdir(file) print 'Is Link? :', os.path.islink(file) print 'Mountpoint? :', os.path.ismount(file) print 'Exists? :', os.path.exists(file) print 'Link Exists?:', os.path.lexists(file) print 

$ ln -s /does/not/exist broken_link $ python ospath_tests.py File : ospath_tests.py Absolute : False Is File? : True Is Dir? : False Is Link? : False Mountpoint? : False Exists? : True Link Exists?: True File : Absolute : False Is File? : False Is Dir? : False Is Link? : False Mountpoint? : False Exists? : False Link Exists?: False File : / Absolute : True Is File? : False Is Dir? : True Is Link? : False Mountpoint? : True Exists? : True Link Exists?: True File : ./broken_link Absolute : False Is File? : False Is Dir? : False Is Link? : True Mountpoint? : False Exists? : False Link Exists?: True

Traversing a Directory Tree¶

os.path.walk() traverses all of the directories in a tree and calls a function you provide passing the directory name and the names of the contents of that directory. This example produces a recursive directory listing, ignoring .svn directories.

import os import os.path import pprint def visit(arg, dirname, names): print dirname, arg for name in names: subname = os.path.join(dirname, name) if os.path.isdir(subname): print ' %s/' % name else: print ' %s' % name print os.mkdir('example') os.mkdir('example/one') f = open('example/one/file.txt', 'wt') f.write('contents') f.close() f = open('example/two.txt', 'wt') f.write('contents') f.close() os.path.walk('example', visit, '(User data)') 

$ python ospath_walk.py example (User data) one/ two.txt example/one (User data) file.txt

os.path Standard library documentation for this module. os The os module is a parent of os.path. File Access Other tools for working with files.

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© Copyright Doug Hellmann. | | Last updated on Jul 11, 2020. | Created using Sphinx. | Design based on «Leaves» by SmallPark |

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Python os.sep – Create Operating System Path Seperator Character

In Python, when working with files and directories, paths are integral to being able to access what you want to access. To create separators which will work for any operating system, you can use the Python os module sep property.

os.sep returns ‘/’ for POSIX and ‘\\’ for Windows.

import os print(os.sep) #Output: '\\'

When working with paths, files and directories in Python, the ability to be able to create code which will work on any operating system is important.

The Python os module has many great functions which help us interact with the operating system of our computer.

One such situation is if you want to build paths which will work on any operating system.

To create separators which will work for any operating system, you can use the Python os module sep property.

os.sep returns ‘/’ for POSIX and ‘\\’ for Windows.

import os print(os.sep) #Output: '\\'

For example, if you want to build a path which looks something like “path/to/file”, you can do the following:

import os path = "path" + os.sep + "to" + os.sep + "file" print(path) #Output: path\to\file

Using this code will work if you have to run it on a different operating system.

One thing to note though is there are better ways you can do the above which will make it easier to maintain and debug.

Using os.path.join() to Build Paths in Python

Another way to build paths in Python is with the os.path.join() function. os.path.join() will join strings together and create a path which will work on any operating system.

os.path.join() is arguably easier to read and also easier to maintain than using os.sepos.path.join() to create a path to a file in Python.

import os path = os.path.join("path","to","file") print(path) #Output: path\to\file

Hopefully this article has been useful for you to learn how about you can use os.sep in Python.

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