Please note I'm not asking "how to check which version of Python did I install".

I've installed several versions of Pythons on my Windows computer, for example Python 2.7-64, Python 2.7-32, and Python 3.7-32.

Python 3 includes "py" and "pyw" which helps me to easily start different Pythons, for example:

• "py -2.7" starts Python 2.7-64
• "py -2.7-32" starts Python 2.7-32
• "py -3.7-32" starts Python 3.7-32

What I'm wondering is, how to check how many different versions of Python did I install on my Windows PC and what versions are they?

PyCharm is able to find it but, for one thing, I don't know if it is a complete list, and for another, I wonder if there is any tool provided by Python or the operating system can do it.

I just got the answer. By typing "py -h" or "py --help" I got the help message:

C:\Users\admin>py -h
Python Launcher for Windows Version 3.7.1150.1013

usage:
py [launcher-args] [python-args] script [script-args]

Launcher arguments:

-2     : Launch the latest Python 2.x version
-3     : Launch the latest Python 3.x version
-X.Y   : Launch the specified Python version
     The above all default to 64 bit if a matching 64 bit python is present.
-X.Y-32: Launch the specified 32bit Python version
-X-32  : Launch the latest 32bit Python X version
-X.Y-64: Launch the specified 64bit Python version
-X-64  : Launch the latest 64bit Python X version
-0  --list       : List the available pythons
-0p --list-paths : List with paths

Which tells me that "-0" (zero, not letter "O") lists the available pythons:

C:\Users\admin>py -0
Installed Pythons found by py Launcher for Windows
 -3.7-64 *
 -3.7-32
 -2.7-64
 -2.7-32

While "-0p" lists not only the versions, but also the paths:

C:\Users\admin>py -0p
Installed Pythons found by py Launcher for Windows
 -3.7-64        C:\Users\admin\AppData\Local\Programs\Python\Python37\python.exe *
 -3.7-32        C:\Users\admin\AppData\Local\Programs\Python\Python37-32\python.exe
 -2.7-64        C:\Python27_64\python.exe
 -2.7-32        C:\Python27_32\python.exe