How to move to one folder back in python
Here is a very platform independent way to do it.
In [1]: os.getcwd()
Out[1]: '/Users/user/Dropbox/temp'
In [2]: os.path.normpath(os.getcwd() + os.sep + os.pardir)
Out[2]: '/Users/user/Dropbox/'
Then you have the path, and you can chdir or whatever with it.
Just like you would in the shell.
os.chdir("../nodes")