How to Restart Python Scripts

Restarting a Python script from within itself can be useful for various reasons: recovering from unrecoverable errors, reloading configuration, or implementing a simple update mechanism.

This guide explains different methods to restart a Python script, emphasizing the recommended approach (os.execv()) and outlining the pros and cons of alternatives.

Restarting with os.execv() (Recommended)

The os.execv() function is the best and safest way to restart a Python script. It replaces the current process with a new one, running the same script. This is much cleaner than launching a new, separate process.

import os
import sys
import time  # Import the time module

def restart():
    print('Restarting script in 3 seconds...') # Clearer output.
    time.sleep(3) # Added delay
    os.execv(sys.executable, [sys.executable] + sys.argv)

restart()
print("This line will NOT be reached in the original process.") # Clarified comment

• sys.executable: This variable holds the absolute path to the Python interpreter (e.g., /usr/bin/python3 or C:\Python39\python.exe).
• sys.argv: This is a list of the command-line arguments passed to the script. sys.argv[0] is the script name itself. We include this so that any arguments your script uses are passed to the restarted version.
• os.execv(executable, args): This is the core of the restart.
• executable: The path to the new program to execute (our Python interpreter).
• args: A list of strings representing the arguments to the new program. We're essentially building the command python your_script.py [any original arguments].
• time.sleep(3): This adds a 3-second delay before restarting. This is often useful to prevent rapid restart loops in case of errors.

You might need to adjust the Python executable name for different systems:

os.execv(sys.executable, ['python3'] + sys.argv)

os.execv(sys.executable, ['py'] + sys.argv)

Restarting with os.system() (Not Recommended)

os.system() executes a command in a new subshell. While you can use it to start a new instance of your script, it's strongly discouraged for restarting.

import os
import time

print('Restarting using os.system()...')
time.sleep(3)
os.system('python main.py')  #  Starts a NEW process.
print("This WILL print, but in the *original* process.") # added a warning

Restarting a Script Indefinitely

To restart a script continuously, combine os.execv() with a while True loop:

import os
import sys
import time

while True:
    print('Running script...')
    time.sleep(3)  # Simulate work being done
    print('Restarting...')
    os.execv(sys.executable, [sys.executable] + sys.argv)

Restarting with psutil (Advanced)

The psutil library provides more control over processes. It's useful for gracefully restarting a script, ensuring file handles and connections are closed. This is a more advanced technique.

import sys
import os
import psutil
import time

def restart_script():
    try:
        p = psutil.Process(os.getpid())
        for handler in p.open_files() + p.connections():
            try:  #  Add a try/except to close each handle.
                os.close(handler.fd)
            except Exception as e:
                print(f"Error closing handle: {e}")
    except Exception as e:
        print(e)

    python = sys.executable
    print("Restarting in 3 seconds...")
    time.sleep(3)
    os.execl(python, python, *sys.argv)


print('Running...')
restart_script()
print("This will NEVER be reached.")

• The code attempts to close all file descriptors and network connections before calling os.execl. The new try/except block is very important to prevent the program from crashing if a file descriptor can not be closed.

Restarting with a Bash Script (Platform-Specific)

For Unix-like systems (Linux, macOS), you can use a bash script to kill any running instances of your script and then start a new one:

pkill -f main.py  # Kill any existing processes running main.py. CAREFUL!
python main.py &  # Run in the background

import os
import subprocess

subprocess.run(['chmod', '+x', 'restart-script.sh'], check=False) # Use check=False because chmod won't work on windows

print('Running main.py...')
os.execl('./restart-script.sh', '&')  # Execute the script
print("This line will NEVER be reached.")