As you say in your question, if you are in a directory /home/usr/one os.chdir('../../'), you will be taken to /home/.
You can confirm this by calling:
os.getcwd()
. . , chdir() .
:
, os.chdir() script , , script . , /home/usr/one script python myscript.py, , os.chdir() script, script; /home/usr/one.