Start Python from Windows PowerShell

I know this looks like a question answered thousands of time, but none of the traditional answers concerning the environment PATH are working.

I want to run the following in Windows 7, in Powershell:

python mycode.py

However, Powershell returns an error, stating that python not recognized as an applet, function, application,...

These are my path variables:

Users variables:

PATH C:\Python27\Lib\site-packages\PyQt4;C:\Python27;C:\Python27\DLLs;C:\Python27\Scripts;C:\Python27\Lib\site-packages\vtk;C:\Python27\gnuplot\binary;C:\Program Files (x86)\pythonxy\SciTE-3.3.2-3;C:\Program Files (x86)\pythonxy\console;C:\MinGW32-xy\bin;C:\Program Files (x86)\pythonxy\swig;C:\Program Files (x86)\pythonxy\gettext\binPATHEXT .PY;.PYWPYTHON_INCLUDE C:\Python27\includePYTHON_LIB C:\Python27\libs\python27.lib

and System variables:

PATHC:\Python27\Lib\site-packages\PyQt4;C:\Python27;C:\Python27\DLLs;C:\Python27\Scripts;C:\Python27\Lib\site-packages\vtk;C:\Python27\gnuplot\binary;C:\Program Files (x86)\pythonxy\SciTE-3.3.2-3;C:\Program Files (x86)\pythonxy\console;C:\MinGW32-xy\bin;C:\Program Files (x86)\pythonxy\swig;C:\Program Files (x86)\pythonxy\gettext\bin;C:\WINDOWS\system32;C:\WINDOWS

I tried the following:

$env:Path = $env:Path +";C:\Python27\"[Environment]::SetEnvironmentVariable("Path", "$env:Path;C:\Python27", "User")

without success. (I tried starting a new Powershell session, of course, and even tried to reboot my PC)

Could it be that PowerShell doesn't properly read the path variable, or I don't have some permission? I am lost, especially knowing that this work fine on another Windows 7 install. I note that typing:

python.exe

...opens a Python terminal as expected.

Edit : Ok I tried the following test.py code :

# -*- coding: utf-8 -*-print "Hello"input()python.exe test.py

open a new terminal with "Hello" in it and wait for my inputbut I don't want that, I expect the normal behaviour, with "Hello" printed in PowerShell, error message in PowerShell and so on.

Edit2 : I noticed that the "Path" variable given in PowerShell by: Get-ChildItem Env

Is not equal to the one in the W7 options "System -> Advanced System settings -> Environment variable" . it was only :

;C:\Python27

Like if my previous command line [Environment]::SetEnvironmentVariable("Path", "$env:Path;C:\Python27")just wrote in it. Fixing this didn't solve my problem either.