constructing absolute path with os.path.join()

Question

I'd like to construct an absolute path in python, while at the same time staying fairly oblivious of things like path-separator.

edit0: for instance there is a directory on the root of my filesystem /etc/init.d (or C:\etc\init.d on w32), and I want to construct this only from the elements etc and init.d (on w32, I probably also need a disk-ID, like C:)

In order to not having to worry about path-separators, os.join.path() is obviously the tool of choice. But it seems that this will only ever create relative paths:

 print("MYPATH: %s" % (os.path.join('etc', 'init.d'),)  MYPATH: etc/init.d 

Adding a dummy first-element (e.g. '') doesn't help anything:

 print("MYPATH: %s" % (os.path.join('', 'etc', 'init.d'),)  MYPATH: etc/init.d 

Making the first element absolute obviously helps, but this kind of defeats the idea of using os.path.join()

 print("MYPATH: %s" % (os.path.join('/etc', 'init.d'),)  MYPATH: /etc/init.d 

edit1: using os.path.abspath() will only try to convert a relative path into an absolute path. e.g. consider running the following in the working directory /home/foo:

 print("MYPATH: %s" % (os.path.abspath(os.path.join('etc', 'init.d')),)  MYPATH: /home/foo/etc/init.d 

So, what is the standard cross-platform way to "root" a path?

 root = ??? # <--  print("MYPATH: %s" % (os.path.join(root, 'etc', 'init.d'),)  MYPATH: /etc/init.d 

edit2: the question really boils down to: since the leading slash in /etc/init.d makes this path an absolute path, is there a way to construct this leading slash programmatically? (I do not want to make assumptions that a leading slash indicates an absolute path)

Answer 1

Using os.sep as root worked for me:

path.join(os.sep, 'python', 'bin') 

Linux: /python/bin

Windows: \python\bin

Adding path.abspath() to the mix will give you drive letters on Windows as well and is still compatible with Linux:

path.abspath(path.join(os.sep, 'python', 'bin')) 

Linux: /python/bin

Windows: C:\python\bin