I have several python versions installed (and working properly on my machines). Isn't there a way to execute a specific version of python from the command line.
Say I want to use python 3.1. I am after something a SIMPLE COMMAND such as python3.1 or python31 that would be used as follows :python3.1 setup.py install, for instance.
[pip has pip3.1 to install a library with the version 3.1 of python, specifically]
Yes, this is possible, but the best approach varies depending on the OS you're using. For Windows, you want the py launcher, for which instructions are here. For Mac OS X and Linux, you could use something like pyenv. Of course, you could always build your own solution using virtualenv.
There are multiple ways to go about this. As Sir_FZ pointed out, the executables are already named python2.7, etc, so what you want already exists. If for some really odd reason you have more than one python2.7 in your $PATH, you can explicitly call /my/other/python2.7 etc. If you're lazy, you can even create alias's alias p2=/my/other/python2.7 and then you can call p2 setup.py install
If you're going to be doing this for more than a day, I'd suggest following one of Sagar's links.
/usr/bin/. Usually, the name of the executables ispython3.4,python2.7...etc so you should already be able to use them in the format you're asking for without any changes.$PATHjust prior to executing the Python code, so that the path to the particular Python version you use is at the front of$PATH.