Question

In python is it possible to get or set a logical directory (as opposed to an absolute one).

For example if I have:

/real/path/to/dir 

and I have

/linked/path/to/dir 

linked to the same directory.

using os.getcwd and os.chdir will always use the absolute path

>>> import os >>> os.chdir('/linked/path/to/dir') >>> print os.getcwd() /real/path/to/dir 

The only way I have found to get around this at all is to launch ‘pwd’ in another process and read the output. However, this only works until you call os.chdir for the first time.

Answer 1

The underlying operational system / shell reports real paths to python.

So, there really is no way around it, since os.getcwd() is a wrapped call to C Library getcwd() function.

There are some workarounds in the spirit of the one that you already know which is launching pwd.

Another one would involve using os.environ['PWD']. If that environmnent variable is set you can make some getcwd function that respects it.

The solution below combines both:

import os from subprocess import Popen, PIPE  class CwdKeeper(object):     def __init__(self):         self._cwd = os.environ.get('PWD')         if self._cwd is None: # no environment. fall back to calling pwd on shell            self._cwd = Popen('pwd', stdout=PIPE).communicate()[0].strip()         self._os_getcwd = os.getcwd         self._os_chdir = os.chdir      def chdir(self, path):         if not self._cwd:             return self._os_chdir(path)         p = os.path.normpath(os.path.join(self._cwd, path))         result = self._os_chdir(p)         self._cwd = p         os.environ['PWD'] = p         return result      def getcwd(self):         if not self._cwd:             return self._os_getcwd()         return self._cwd  cwd = CwdKeeper() print cwd.getcwd() # use only cwd.chdir and cwd.getcwd from now on.     # monkeypatch os if you want: os.chdir = cwd.chdir os.getcwd = cwd.getcwd # now you can use os.chdir and os.getcwd as normal.