Coexistence of Python 2.x and 3.x on same OS

[Edward Diener]

On 10/5/2012 5:32 PM, Dennis Lee Bieber wrote:
> On Fri, 05 Oct 2012 08:15:30 -0400, Edward Diener
> <eldiener at tropicsoft.invalid> declaimed the following in
> gmane.comp.python.general:
>
>>
>> Windows installs of Python do not distinguish releases by Pythonx(.x)
>> but just install different versions of Python in different directories.
>
> 	Really?
>
> E:\Python27>dir
>   Volume in drive E is Data
>   Volume Serial Number is 2626-D991
>
>   Directory of E:\Python27
>
> 08/28/2012  05:32 PM    <DIR>          .
> 08/28/2012  05:32 PM    <DIR>          ..
> 08/28/2012  02:11 PM    <DIR>          DLLs
> 08/28/2012  05:43 PM    <DIR>          Doc
> 08/28/2012  02:11 PM    <DIR>          include
> 08/31/2012  04:58 PM    <DIR>          Lib
> 08/28/2012  02:11 PM    <DIR>          libs
> 08/28/2012  02:15 PM           108,255 matplotlib-wininst.log
> 08/28/2012  02:18 PM             4,169 MySQL-python-wininst.log
> 08/28/2012  02:15 PM            98,498 numpy-wininst.log
> 08/28/2012  02:20 PM            17,816 PIL-wininst.log
> 08/28/2012  03:29 PM             1,572 PyOpenGL-accelerate-wininst.log
> 08/28/2012  03:38 PM             3,009 pyserial-wininst.log
>
> 06/24/2011  12:38 PM            27,136 python.exe		****
> 06/24/2011  12:38 PM            27,136 python2.7.exe	****
> 06/24/2011  12:38 PM            27,136 python2.exe	****
>
> 08/28/2012  05:32 PM            90,943 PythonCard-wininst.log
>
> 06/24/2011  12:38 PM            27,136 pythonw.exe	****
> 06/24/2011  12:38 PM            27,136 pythonw2.7.exe	****
> 06/24/2011  12:38 PM            27,136 pythonw2.exe	****

That's, as you say, ActievState. The normal Python installer does not 
create a python2.7.exe etc.

But of course I can create any links I want, so that's not really the 
problem. The major difficulty is that prior to invoking either "python" 
directly or a script with a normal Python file association, I want to be 
able to specify which version of Python should be invoked as the default 
without having to specifically invoke a partiocular version  by typing 
'python2.7 ...' or 'python3.3 ...' etc.

>
> 08/28/2012  02:15 PM           196,096 Removematplotlib.exe
> 08/28/2012  02:18 PM           196,096 RemoveMySQL-python.exe
> 08/28/2012  02:15 PM           196,096 Removenumpy.exe
> 08/28/2012  02:20 PM           196,096 RemovePIL.exe
> 08/28/2012  03:29 PM           196,096 RemovePyOpenGL-accelerate.exe
> 08/28/2012  03:38 PM           196,096 Removepyserial.exe
> 08/28/2012  05:32 PM            61,440 RemovePythonCard.exe
> 08/28/2012  02:20 PM           196,096 Removereportlab.exe
> 08/28/2012  02:19 PM           196,096 Removescipy.exe
> 08/28/2012  05:29 PM           196,096 RemoveWConio.exe
> 08/28/2012  02:20 PM            40,362 reportlab-wininst.log
> 08/28/2012  02:19 PM           159,420 scipy-wininst.log
> 08/28/2012  05:32 PM    <DIR>          Scripts
> 08/28/2012  02:11 PM    <DIR>          tcl
> 08/28/2012  02:11 PM    <DIR>          Tools
> 11/28/2007  04:32 PM           258,352 unicows.dll
> 06/24/2011  12:38 PM            49,664 w9xpopen.exe
> 08/28/2012  05:29 PM               891 WConio-wininst.log
>                28 File(s)      2,822,071 bytes
>                10 Dir(s)  148,557,684,736 bytes free
>
> E:\Python27>
>
> 	That's what was set up by a recent ActiveState installer (well,
> recent for me -- I'd still been using 2.5 three months ago)
>
> 	Yes, it IS in a version numbered directory, but there are copies of
> the executable named as plain python, pythonX, and pythonX.Y
>
> E:\Python27>cd %homepath%
>
> E:\UserData\Wulfraed\My Documents>python
> ActivePython 2.7.2.5 (ActiveState Software Inc.) based on
> Python 2.7.2 (default, Jun 24 2011, 12:21:10) [MSC v.1500 32 bit
> (Intel)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
>>>> ^Z
>
>
> E:\UserData\Wulfraed\My Documents>python2.7
> ActivePython 2.7.2.5 (ActiveState Software Inc.) based on
> Python 2.7.2 (default, Jun 24 2011, 12:21:10) [MSC v.1500 32 bit
> (Intel)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
>>>>
>
> 	Granted, one would need to have each installation directory in the
> PATH, ordered such that the preferred version would be found first when
> using just "python".

There is much more than just the PATH needed to change to have a 
different Python be the default. File associations also. I thnk there 
are more things too, but I know it has always been difficult on Windows 
to easily change which distribution is called when "python" is executed 
or some Python file association is executed.

I welcome the new Python launcher for Windows mentioned but have not had 
a chance to use it and see how it works yet. I will try it this weekend 
and hopefully it will work well to solve the problem of having multiple 
Python installations installed on Windows at the same time, and being 
able to easily specify the one I want invoked.