watcher.py

#Cross-platform file watcher.  Originally forked from:
#https://stackoverflow.com/questions/182197/how-do-i-watch-a-file-for-changes/49007649#49007649
import os
import sys 
import time
import importlib

class Watcher(object):
    running = True
    refresh_delay_secs = 1

    # Constructor
    def __init__(self, watch_file, call_func_on_change=None, *args, **kwargs):
        self._cached_stamp = 0
        self.filename = watch_file
        self.call_func_on_change = call_func_on_change
        self.args = args
        self.kwargs = kwargs

    # Look for changes
    def look(self):
        stamp = os.stat(self.filename).st_mtime
        if stamp != self._cached_stamp:
            self._cached_stamp = stamp
            # File has changed, so do something...
            print('File changed')
            if self.call_func_on_change is not None:
                self.call_func_on_change(*self.args, **self.kwargs)

    # Keep watching in a loop        
    def watch(self):
        while self.running: 
            try: 
                # Look for changes
                time.sleep(self.refresh_delay_secs) 
                self.look() 
            except KeyboardInterrupt: 
                print('\nDone') 
                break 
            except: 
                import traceback
                print('Unhandled error: %s, %s' % (sys.exc_info()[1],sys.exc_info()[2]) )
                print("Traceback:")
                traceback.print_exc()

# Call this function each time a change happens
def custom_action(text):
    # importlib is python >= 3.4 only    
      import ibuild
    #try:
      print("reloading")
      importlib.reload(ibuild)

    #except 'NameErrorx':
      #print("initial load")
      #import ibuild
      #print("initial load complete")

watch_file = 'ibuild.py'

print('Starting watch on file %s' % watch_file)
# watcher = Watcher(watch_file)  # simple
watcher = Watcher(watch_file, custom_action, text='yes, changed')  # also call custom action function
watcher.watch()  # start the watch going