Invoking a PowerShell script from Python

Question

I'm trying to start a PowerShell script from python like this:

psxmlgen = subprocess.Popen([r'C:\WINDOWS\system32\WindowsPowerShell\v1.0\powershell.exe',
                             './buildxml.ps1',
                             arg1, arg2, arg3], cwd=os.getcwd())
result = psxmlgen.wait()

The problem is that I get the following error:

File C:\Users\sztomi\workspace\myproject\buildxml.ps1 cannot be loaded because the execution of scripts is disabled on this system. Please see "get-help about_signing" for more details.

DESPITE the fact that I did enable running scripts in Powershell a long time ago by typing Set-ExecutionPolicy Unrestriced in an administrator-ran PS terminal (and did again, just to make sure). The powershell executable is the same that the shortcut in start menu points to. Get-ExecutionPolicy correctly reports Unrestricted no matter if I ran PowerShell as admin or not.

How can I execute a PS script correctly from Python?

Answer 1

First, Set-ExecutionPolicy Unrestriced is on a per user basis, and a per bitness basis (32-bit is different than 64-bit).

Second, you can override the execution policy from the command line.

psxmlgen = subprocess.Popen([r'C:\WINDOWS\system32\WindowsPowerShell\v1.0\powershell.exe',
                             '-ExecutionPolicy',
                             'Unrestricted',
                             './buildxml.ps1',
                             arg1, arg2, arg3], cwd=os.getcwd())
result = psxmlgen.wait()

Apparently you can access the 64-bit PowerShell from 32-bit PowerShell with this path (thanks to @eryksun in comments):

powershell64 = os.path.join(os.environ['SystemRoot'], 
    'SysNative' if platform.architecture()[0] == '32bit' else 'System32',
    'WindowsPowerShell', 'v1.0', 'powershell.exe')

Answer 2

For those of us who wanted to know how to display the values of arg1, arg2 and arg3 after it was passed to powershell, all you need to do is:

Write-Host $args[0]
Write-Host $args[1]
Write-Host $args[2]