What's the best way to execute PowerShell scripts from Python

Question

All the previous posts on this topic deal with specific challenges for their use case. I thought it would be useful to have a post only dealing with the cleanest way to run PowerShell scripts from Python and ask if anyone has an better solution than what I found.

What seems to be the generally accepted solution to get around PowerShell trying to interpret different control characters in your command differently to what's intended is to feed your Powershell command in using a file:

ps = 'powershell.exe -noprofile'
pscommand = 'Invoke-Command -ComputerName serverx -ScriptBlock {cmd.exe \
/c "dir /b C:\}'
psfile = open(pscmdfile.ps1, 'w')
psfile.write(pscommand)
psfile.close()
full_command_string = ps + ' pscmdfile.ps1'
process = subprocess.Popen(full_command_string , shell=True, \
stdout=subprocess.PIPE, stderr=subprocess.PIPE)

When your python code needs to change the parameters for the Powershell command each time you invoke it you end up writing and deleting a lot of temporary files for subprocess.Popen to run. It works perfectly but it's unnecessary and not very clean. It's really nice to be able to tidy up and wanted to get suggestions on any improvements I could make to the solution I found.

Instead of writing a file to disk containing the PS command create a virtual file using the io module. Assuming that the "date" and "server" strings are being fed in as part of a loop or function that contains this code, not including the imports of course:

import subprocess
import io
from string import Template
raw_shellcmd = 'powershell.exe -noprofile '

--start of loop with server and date variables populated--

raw_pslistcmd = r'Invoke-Command -ComputerName $server -ScriptBlock ' \
        r'{cmd.exe /c "dir /b C:\folder\$date"}'

pslistcmd_template = Template(raw_pslistcmd)
pslistcmd = pslistcmd_template.substitute(server=server, date=date)
virtualfilepslistcommand = io.BytesIO(pslistcmd)
shellcmd = raw_shellcmd + virtualfilepslistcommand.read()

process = subprocess.Popen(shellcmd, shell=True, stdout=subprocess.PIPE, \
stderr=subprocess.PIPE)

--end of loop--

Answer 1

Arguably the best approach is to use powershell.exe -Command rather than writing the PowerShell command to a file:

pscommand = 'Invoke-Command ...'
process = subprocess.Popen(['powershell.exe', '-NoProfile', '-Command', '"&{' + pscommand + '}"'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)

Make sure double quotes in the pscommand string are properly escaped.

Note that shell=True is required only in certain edge cases, and should not be used in your scenario. From the documentation:

On Windows with shell=True, the COMSPEC environment variable specifies the default shell. The only time you need to specify shell=True on Windows is when the command you wish to execute is built into the shell (e.g. dir or copy). You do not need shell=True to run a batch file or console-based executable.