Parallel Python x.y.A and x.y.B installations on a single Windows machine

[Ned Batchelder]

On Monday, November 25, 2013 7:32:30 AM UTC-5, Jurko Gospodnetić wrote:
> Hi all.
> 
>    I was wondering what is the best way to install multiple Python 
> installations on a single Windows machine.
> 
>    Regular Windows installer works great as long as all your 
> installations have a separate major.minor version identifier. However, 
> if you want to have let's say 2.4.3 & 2.4.4 installed at the same time 
> it does not seem to work.
> 
>    I have not been able to find any prepackaged Python installation or 
> really any solution to this. Most of the advice seems to boil down to 
> 'do not use such versions together, use only the latest'.
> 
>    We would like to run automated tests on one of our projects (packaged 
> as a Python library) with different Python versions, and since our code 
> contains workarounds for several problems with specific Python patch 
> versions, we'd really like to be able to run the tests with those 
> specific versions and with as little fuss as possible.
> 
>    Looking at what the Python installer does, the only problematic part 
> for working around this manually seems to be the registry entries under 
> 'Software\Python\PythonCore\M.m' where 'M.n' is the major.minor version 
> identifier. If Python interpreter expects to always find its entries 
> there, then I guess there is no way to do what we need without building 
> customized Python executables. Is there a way to force a specific Python 
> interpreter to not read in this information, read it from an .ini file 
> or something similar?
> 
>    Many thanks.
> 
>    Best regards,
>      Jurko Gospodnetiďż˝

IIRC, Python itself doesn't read those registry entries, except when installing pre-compiled .msi or .exe kits.  Once you have Python installed, you can move the directory someplace else, then install another version of Python.

If you need to use many different Pythons of the same version, this script helps manage the registry: http://nedbatchelder.com/blog/201007/installing_python_packages_from_windows_installers_into.html

--Ned.