Hot reload a python working script (compatible with both python 2 & 3)

hot_reload.py

#!/usr/bin/python
from __future__ import print_function
import sys, os, time, threading, subprocess, fnmatch


class SourceChangeMonitor(threading.Thread):
    # Remember the process ID of the subprocess for when
    # we want to restart it
    _process = None

    # How often should we check for changes (in seconds)
    POLL_INTERVAL = 1

    # Which files should be monitored for changes?
    # Here, we deliberately exclude files beginning with a dot (.)
    FILE_PATTERN = r"[!.]*.py"

    # Which directory is the root of the source files?
    ROOT_DIRECTORY = r"/type/script/path/here/"

    # Entry point program to run
    PROGRAM = r"name_of_script.py"

    def __init__(self):
        threading.Thread.__init__(self)
        self.this_script_name = os.path.abspath(sys.argv[0])
        self.files = self.get_files()
        self.start_program()

    def run(self):
        while 1:
            time.sleep(self.POLL_INTERVAL)
            if self.poll():
                print("-------------------------------------------------")
                print("Noticed a change in program source. Restarting...")
                print("-------------------------------------------------")
                self.start_program()

    def get_files(self):
        """
        Get a list of all files along with their timestamps for last modified
        """
        files = []
        for root, dirnames, filenames in os.walk(self.ROOT_DIRECTORY):
            for filename in fnmatch.filter(filenames, self.FILE_PATTERN):
                full_filename = os.path.join(root, filename)
                files.append(full_filename)

        # Attach the last modified dates
        files = map(lambda f: (f, os.stat(f).st_mtime), files)
        files = [filename_mtime for filename_mtime in files if filename_mtime[0] != self.this_script_name]
        return files

    def poll(self):
        """Check if any source files have changed since last poll. Returns True if files have changed, False otherwise"""
        new_files = self.get_files()
        if self.files != new_files:
            self.files = new_files
            return True
        return False

    def start_program(self):
        """Start the program. If it was already started, kill it before restarting"""
        if self._process != None and self._process.poll() is None:
            self._process.kill()
            self._process.wait()

        self._process = subprocess.Popen([sys.executable, self.PROGRAM])


if __name__ == "__main__":
    SourceChangeMonitor().start()