Auto-reload turtle code on file save (https://docs.python.org/3/library/turtle.html)

watch_turtle.py

"""Reloads the `my_turtle.py` code on save.

Put simple turtle instructions in the `my_turtle.py` file,
and they'll be re-run (on a clean window) on each file save.

Usage:
1/ put some turtle instructions in a `my_turtle.py` file
   (eg `turtle.forward(100)`)
2/ run `python watch_turtle.py` on a commandline
   (no dependencies needed)
3/ play around by adding/modifiying some turtle instructions
   in the `my_turtle.py` file
4/ when you're happy with your modifications, save the file
   (it'll empty the turtle screen and re-run the instructions)
5/ back to 3/

Stop by pressing CTRL+C in the terminal.
"""
import os
import traceback
import sys
import time
import turtle

# Get the last modification time. Not as effective as some
# libs out there, but doesn't needs dependencies.
get_last_mod = lambda: os.stat('my_turtle.py').st_mtime

# Fancier than the original arrow shape.
turtle.shape('turtle')

# Initialize with a dummy value.
last_modification = 0

while True:  # Run until a KeyboardInterrupt (CTRL+C).
    try:
        if get_last_mod() != last_modification:
            # Has the `my_turtle.py` file been saved?
            print('Reloading...')
            last_modification = get_last_mod()
            # Empty the window, start from scratch.
            turtle.reset()
            # Re-run the instructions in the `my_turtle.py` file.
            with open('my_turtle.py', 'r') as my_turtle:
                exec(my_turtle.read())
        time.sleep(1)  # Poll once a second.
    except KeyboardInterrupt:  # CTRL+C in the terminal.
        print('Bye!')
        sys.exit()
    except:
        # Anything wrong in the `my_turtle.py` file?
        # Don't fail, just display the traceback, and continue.
        print(traceback.format_exc())