How to find python installation directory on Ubuntu

First question:

which python though its usually /usr/bin/python for the 2.7

Second question:

From a terminal & python2.7: python2.7 yourfile.py.
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.

I hope this was helpful.

If you want to find the location of a program you can just use whereis <program>.

In your case run:

whereis python2.7
whereis python3.2

For finding every file that apt-get has copied for installation use:

dpkg -S python2.7
dpkg -S python3.2

But maby it is recommend to save it in a textfile, because the output is to large.

dpkg -S python2.7 >log.txt
gedit log.txt

for running .py file with python 3.2

python3.2 <file.py>

Here is a simple way, run in terminal:

type -a python

or

type -a python3