http://docs.python.org/library/os.html
os.getcwd()ΒΆ
Return a string representing the current working directory. Availability: Unix, Windows.

http://stefaanlippens.net/getcwd
import os
print os.getcwd()

import sys, os
print sys.path[0]

will print the directory where this script resides.
additionally you can use

sys.argv[0]

to get the filename of the script. to join the two do

os.path.join(sys.path[0], sys.argv[0])