How to call a shell command fom pythonw (with no explorer.exe running) without a terminal window flashing?

Question

I am running a Python program on Windows with:

• no explorer.exe running, no desktop, no start menu, typical for embedded computers. If you want to try, you can emulate this by killing explorer.exe in the Task manager ; note that I do it differently but out of topic here
• pythonw.exe instead of python.exe to avoid a to have a cmd.exe terminal window

If you run pythonw test.py with

import os
os.system("shutdown /r /t 3600")

you will see a terminal window flashing during < 1 second.

Same problem with subprocess.call(...).

Same problem with subprocess.run(...) like in Is there a command in Python for instant shutdown on Windows 10?.

(Note: if explorer.exe is killed, you can call the Task Manager with CTRL+SHIFT+ESCAPE and Run command to launch pythonw test.py)

Question: How to call Windows tools like shutdown with 1) no explorer.exe 2) pythonw.exe, without seeing a cmd.exe window flashing?

Answer 1

The solution is:

import subprocess

# restart
subprocess.Popen(r"C:\Windows\System32\shutdown.exe /r /t 0", creationflags=subprocess.CREATE_NO_WINDOW)

# power off
subprocess.Popen(r"C:\Windows\System32\shutdown.exe /p", creationflags=subprocess.CREATE_NO_WINDOW)

Context (pasted from @Mofi's comments):

os.system is declared as deprecated since more than 10 years and should not be used anymore at all. There is the subprocess module which gives a Python script writer the full control on Windows how an executable is run by calling the Windows kernel library function CreateProcess without or with a STARTUPINFO structure.

os.system() calls the system function which on Windows results in calling CreateProcess with %ComSpec% (defined with %SystemRoot%\System32\cmd.exe expanding usually to C:\Windows\System32\cmd.exe) with the option /c (run command line and close) and the command line passed as argument to os.system appended as additional arguments for cmd.exe.

In this case cmd.exe searches for a file with name shutdown in the current directory and next in the directories as listed in local environment variable PATH with no file extension at all or with a file extension as listed in local environment variable PATHEXT. It hopefully finds in this case after several file system accesses %SystemRoot%\System32\shutdown.exe and calls now CreateProcess to run this batch file with using the standard streams of cmd.exe and waiting for self-termination of shutdown.exe after which cmd.exe closes itself.

There can be used os.environ to get the string value of the environment variable SystemRoot. This directory path string can next be concatenated with the string "\\System32\\shutdown.exe" to get the fully qualified file name of the executable to run. It is very unlikely that the environment variable SystemRoot is not defined at all. That is possible only if a user explicitly deletes this environment variable in a command prompt window before starting in same command prompt window Python for interpreting a Python script.

There should be used the string "C:\\Windows" in case of environ["SystemRoot"] returns no string (or an empty string). However, it is advisable to check the existence of finally determined fully qualified file name of the Windows command SHUTDOWN and inform the user if the executable is not existing instead of a blind execution of this executable and hoping it really exists although this is most likely always the case (at least now but who knows the future). Then subprocess.Popen() can be used to run shutdown.exe with its full path.

subprocess.Popen() offers subprocess.CREATE_NO_WINDOW for calling CreateProcess with the Process Creation Flag CREATE_NO_WINDOW set in dwCreationFlags for not opening a new console window for the Windows console application shutdown.exe.