[Tutor] Installing python

[Steven D'Aprano]

On Fri, Nov 02, 2018 at 02:13:46PM -0700, Roger Lea Scherer wrote:
> Hey,
> 
> I have installed python 3.7 on my computer Windows10
> (C:\Users\Roger\AppData\Local\Programs\Python\Python37), but when I go to
> the git repository that holds all my projects and type "python --version"
> in WindowsPowershell, I get Python 3.6.5.

What happens if you type "python37 --version" instead?

What happens if you call the Python launcher instead? Try this and see 
what it does:

py -V

https://docs.python.org/3/using/windows.html#launcher


> So I guess my question is am I supposed to install python 3.7 in the git
> repository?

Heavens no.


> I guess I'm so used to installing programs in Windows or Mac and having
> them accessible globally (I guess is the word) that I expected python 3.7
> to do the same thing, 

I expect it is accessible globally, but you need to know what to call 
it. I'm not a Windows expert, but I expect that it will be more or less 
equivalent to other OSes in the sense that when you call a program by 
name (say, "notepad", or "python") it searches a list of known program 
locations (probably recorded in the Registry) for a matching name, and 
runs the first one found.

I expect that you have entries for 

python36
python37

and probably others, plus an alias for "python" which points to 
python36. You may be able to change the alias, but I don't know how you 
do that on Windows.

Or just be explicit about the one you want.

Or use the "py" Windows launcher, which is supposed to manage all that 
for you. (I don't know how well it works.)


> although I understand about programs written earlier
> crashing because of upgrades, like from 2.7 to 3.4 for instance.

They shouldn't *crash* the interpreter. If they do, that's a bug in the 
interpreter. They might *raise an exception*.

The difference is that a crash (a segfault or core dump) is the 
interpreter melting down and exploding, while an exception is a nicely 
controlled shut down.


Hope this helps shed some light on what's going on.



-- 
Steve