In PowerShell, Get-Command python | fl * will tell you which Python executable it's finding and show you details about where it is.

1. You can check Settings -> Apps and Features, or Control Panel -> Programs and Features. They will show you distinct versions of Python you installed, but that might not be enough if Python is installed as part of some other toolkit or program.
2. If Python 2.7.11 is there, select it and click uninstall. If it's not there, see if you can tell what it's installed with, from the output of Get-Command earlier, and decide if you want to remove that.
3. How PowerShell chooses what to run when you type a command is explained in help about_Command_Precedence, and is:
   1. Alias
   2. Function
   3. Cmdlet
   4. Native Windows commands

At the point of "Native Windows commands", it goes to the PATH environment variable, a semi-colon separated list of path names, which get searched in order, looking for a matching executable file.

You can see the folders with:

$Env:PATH -split ';'

And you can watch PowerShell identify what to run for 'python' with the command

Trace-Command –Name CommandDiscovery –Expression {get-command python} -PSHost

So, to make Python 2.7.13 the one to launch, you could:

• make it the only Python version available.
• move its folder to the front of the PATH list, ahead of any other version. See: What are path and other environment variables, and how can I set or use them - question on SuperUser.com
• make a batch file to launch it called python.bat in a folder in the PATH ahead of other versions.
• make an alias (in your PS Profile) named python to launch the one you want (New-Alias -name python -Value C:\Python27\python.exe , etc).

In powershell, enter the following:

$Env:PY_PYTHON = 2

Then try using the command "py". It should start up Python 2.7. If you ever want to run Python 3.3 again, "py -3" will do the trick.

This is most likely due to the path variable. You can see this in a command window by typing

Path

at your prompt.

To update the settings,

1. Open the 'System' properties.

2. Open Environment Variables

3. Highlight the 'Path' Variable and click edit.

4. Edit the values for the Python entries, to point to the desired python version.

5. OK on all boxes, close any CMD windows open, and open new one. Python command should now reference the correct location.

Solution refers to Windows 10, but is essentially the same on Windows 7 +

Possibly because after python 3.3 intended command is not python, but simply py
Detailed explanation here

And short answer to your question:
check if powershell command py -0p --list-paths finds any versions.

Hi @EMP_H ,

Yes, you should be able to switch between python versions. As a standard, it is recommended to use the python3 command or python3.7 to select a specific version. The py.exe launcher will automatically select the most recent version of Python you've installed. You can also use commands like py -3.7 to select a particular version, or py --list to see which versions can be used. HOWEVER, the py.exe launcher will only work if you are using a version of Python installed from python.org. When you install Python from the Microsoft Store, the py command is not included. Since you're using the Microsoft Store version of Python, you should use the python3 (or python3.7) command.

Hope that helped. Please let us know if you have further questions.

Best,
Grace

For information please read this FAQ doc for using python on windows.