Installing Python 3 on Windows

[eryk sun]

On Tue, Aug 2, 2016 at 12:11 PM, Uri Even-Chen <uri at speedy.net> wrote:
>
> I want to install Python 3 on Windows, but I also need Python 2 for Google
> App Engine SDK. When I type a name of a Python file in command line, I want
> it to run with Python 3. However, I checked with "print 3/5" and it printed
> 0 - Python 2. I have the latest versions of Python installed
> - python-2.7.12.msi and python-3.5.2.exe
>
>>python --version
> Python 2.7.12
>
>>assoc .py
> .py=Python.File
>
>>ftype Python.File
> Python.File="C:\Python27\python.exe" "%1" %*

Open the control panel's "Programs and Features". Look for the most
recently installed "Python Launcher"; right-click it and select
"Repair". That should fix the Python.File and Python.NoConFile
commands. If these commands aren't your current choice in Explorer,
open Default Programs->Set Associations. Change the association for
.py and .pyw to "Python". If there are multiple "Python" entries in
the list, the icon of the correct one should have a rocket (a
launcher) in the upper left-hand corner.

The launcher handles shebangs and even accepts common Unix paths such
as /usr/bin, e.g.:

Latest 2.x:  #! /usr/bin/python
Latest 3.x:  #! /usr/bin/python3

Without a shebang the launcher currently defaults to Python 2 if it's
installed. To always use Python 3 as the default, set the environment
variable `PY_PYTHON=3`.

> By the way, i[s] there a way to print the Python version from Python?

sys.version is the version string. sys.version_info is a named
sequence of version information:

    >>> sys.version_info
    sys.version_info(major=2, minor=7, micro=12, releaselevel='final', serial=0)
    >>> sys.version_info[:]
    (2, 7, 12, 'final', 0)

    >>> sys.version_info
    sys.version_info(major=3, minor=5, micro=2, releaselevel='final', serial=0)
    >>> sys.version_info[:]
    (3, 5, 2, 'final', 0)