[Tutor] Installing both Python 2.7 and Python 3.4 on Windows 7 Pro 64-bit: Install Python 2.7 FIRST!

[boB Stepp]

On Fri, Oct 10, 2014 at 7:43 AM, boB Stepp <robertvstepp at gmail.com> wrote:
> On Fri, Oct 10, 2014 at 2:05 AM, Wolfgang Maier
> <wolfgang.maier at biologie.uni-freiburg.de> wrote:
>> On 10/10/2014 05:57 AM, boB Stepp wrote:
[...]
>>
>> It would help if you could share details about how you tried to run the
>> Python 3 program (command line call, double-click, Python launcher for
>> Windows, ..).
>>
> Initially, I ran the program in question by double-clicking on its
> icon, which was my normal way of running it. This is when I realized I
> had a problem. The program would run without error, but give erroneous
> print and input statement results. I next put Python 3 into my path
> variable, but the same error persisted. From the command line I found
> that if I ran it normally (With Python 3 still in the path like it was
> on my previous 3.4.1 installation.), meaning
>
> python program_name.py
>
> it behaved the same way as double-clicking on the icon. However, if I ran it as
>
> py -3 program_name.py
>
> then all was well.
>
> Apparently Python 2.7.8 became the system default installation if I
> installed it last, but after uninstalling both and installing Python
> 3.4.2 last, it became the default. Or, at least when double-clicked on
> it ran normally.
>
> I have since added shebang lines to my programs specifying Python 3.
>
> I hope I have not forgotten any relevant details!
>
Apparently I must have forgotten relevant details because I have
concluded tonight that I have not solved anything. Despite thinking
that I had made Python 3.4.2 my default Python, I am now certain that
Python 2.7.8 is, in fact, my current default Python. So switching the
order of installation did not work and whatever I did last night in my
presumably sleepy or lame state was not what I thought I was doing. If
I double-click on a file or icon to run a program, it runs under
Python 2.7.8. If I run it from the command line with py
program_name.py, then it runs under Python 2.7.8. This is with shebang
lines removed from all programs.

So I apologize for what I wrote earlier.

I can live with 2.7.8 being the default Python, but if I wanted to
make 3.4.2 the default, how would I go about doing it?

boB