is python installed
Simailarly for 3.2: python3.2 yourfile.py though 3.2 isn't installed by default. (You can apt-get install python3.2 .). What python yourfile.py will do depends on which alternative is used for your python interpreter. You can change that by issuing update-alternatives python as root (or by using su). Third question: Environment variables are shell dependent, though you can write them out with echo $variable and set them with variable=value (from bash). The search path is simply called PATH and you can get yours by typing echo $PATH.