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).

Since, you are able to run Python in PowerShell. You can just do python <scriptName>.py to run the script. So, for a script named test.py containing

name = raw_input("Enter your name: ")
print "Hello, " + name

The PowerShell session would be:

Start:

cd C:\Python27
python test.py

Session transcript:

Enter your name: Monty Python
Hello, Monty Python

In PowerShell, where is an alias for the Where-Object cmdlet.

To explicitly invoke where.exe, include the .exe extension:

PS ~> where.exe python
C:\Users\mathias\AppData\Local\Microsoft\WindowsApps\python.exe

If you want to figure out why a certain command name doesn't resolve as expected, use Get-Command:

PS ~> Get-Command where

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Alias           where -> Where-Object


PS ~> Get-Command where*

CommandType Name                  Version      Source
----------- ----                  -------      ------
Alias       where -> Where-Object
Cmdlet      Where-Object          3.0.0.0      Microsoft.PowerShell.Core
Application where.exe             10.0.19041.1 C:\WINDOWS\system32\where.exe

As an amusing bonus, your newfound knowledge of Get-Command might prove where.exe obsolete - as Get-Command evidently has the ability to locate executables as well :)

PS ~> Get-Command python
    
CommandType Name       Version Source
----------- ----       ------- ------
Application python.exe 0.0.0.0 C:\Users\mail\AppData\Local\Microsoft\WindowsApps\python.exe

You have a file named python located at C:\Users\Admin, and it isn't an executable file(.exe), the file isn't what you are looking for and it can be opened by the programs shown in the dialog, I infer from the programs the extension is either .xml or .pdf, though it is more likely to be .xml.

You can run python in cmd without typing its full path but can't do so in PowerShell is because PowerShell doesn't find the path of the .exe, you likely installed Python to C:\Program Files\Python39, and the folder is added to system path variable and NOT user path, then you must have run cmd as admin so it has access to system path and finds python.exe.

However from the folder path the shell is currently at, you likely haven't started PowerShell as admin, so it doesn't have access to system path and can not find python.exe.

The solution: run powershell as admin.

Also, don't use the default PowerShell, you are missing a lot if you don't use PowerShell 7.

Try setting the path this way:

 $env:path="$env:Path;C:\Python27"

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.

Edit the PATHEXT environment variable and add the .py extension.

Just add this line to your PowerShell profile:

$env:PATHEXT += ";.py"

or you could just edit PATHEXT globally in the system settings (just search in the Start menu for "environment" and choose the option for "Edit environment variables for your account").