Do I have to uninstall old python versions to update to a new one on Windows?

Question

I have python 3.2 installed and I want to know if I have to uninstall earlier versions before installing newer ones.

Answer 1

Install all the Python X.Y versions you want, but include Python 3.3 or later (last is best, or reinstall it after all the others) to get the Python Launcher that @abarnert mentioned in his comments. It is also available as a standalone installer.

Earlier versions than 3.3 should not register extensions, so the launcher installed by 3.3 or later will remain the default handler for .py files.

From the command line:

py -2        # launch latest 2.x version installed.
py -3        # latest 3.x
py -3.2      # run exact version
py -3.2-32   # run 32-bit version on 64-bit system.

So you can even have mixed 32-bit and 64-bit installations.

The environment variable PY_PYTHON can be set to specify the default Python to run.

In scripts, add a comment of the following forms below to use that version of Python when the script is double-clicked or run from command line via py script.py:

#!python2
#!python3
#!python3.2
#!python3.2-32

See PEP 397 for further details.