How to chose python executable if several exist?

I would like to execute Python scripts using the Python/C API (I am using Mac OS X Mavericks, Xcode). Since multiple Python distributions are installed on my machine (System, Homebrew, several virtualenvs), how can I define which to use?

Solution

You can define which one to use either:

by specifying the fullpath to the executable ;
or with different aliases.

For example, I have both Python 2.7 and Python 3.2 on this machine:

$ python
Python 2.7.3 (default, Dec 18 2012, 13:50:09)
[GCC 4.5.3] on cygwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

$ python3
Python 3.2.3 (default, Jul 23 2012, 16:48:24)
[...]

$ /usr/bin/python2.7
Python 2.7.3 (default, Dec 18 2012, 13:50:09)
[...]

$ /usr/bin/python3.2
Python 3.2.3 (default, Jul 23 2012, 16:48:24)
[...]