How to Run and Control External Programs in Python on Windows

Method 1: Using os.system()

The os.system(command) function runs an external program or script; command is a string containing the executable and any arguments separated by spaces.

command – the command line to execute, with parameters separated by spaces.

Method 2: Using ShellExecute via win32api

Another way is to call ShellExecute(hwnd, op, file, args, dir, show) from the win32api module. Parameters:

hwnd – handle of the parent window (0 if none)

op – operation to perform, e.g., "open", "print", or empty

file – the program or script to run

args – arguments passed to the program (empty for files)

dir – initial working directory of the program

show – whether to display the window

Method 3: Creating a Process with win32process

For finer control you can create a process using

CreateProcess(appName, cmdLine, procAttr, threadAttr, inheritHandle, creationFlags, newEnv, currentDir, attr)

. Parameters:

appName – executable file name

cmdLine – command‑line arguments

procAttr – process security attributes

threadAttr – thread security attributes

inheritHandle – inheritance flag

creationFlags – creation flags

newEnv – environment block (or None)

currentDir – current directory for the process

attr – additional attributes

To terminate a process you can call TerminateProcess(handle, exitCode), where handle is the process handle and exitCode is the exit code.

You may also wait for a thread to finish with WaitForSingleObject(handle, milliseconds); milliseconds is the timeout (‑1 means infinite).

Method 4: Calling kernel32.dll Functions with ctypes

The ctypes module lets Python call functions in dynamic libraries such as kernel32.dll. It provides C‑compatible data types and can invoke functions like MessageBoxA from user32.dll. The module works on Windows, Linux, and macOS.

Example: calling MessageBoxA from user32.dll to display a message box.

Note: Install the pywin32 package (e.g., pywin32‑216.win‑amd64‑py2.7) to use the win32 APIs on a 64‑bit Windows system.