Run python script when txt file is changed

Question

I am working on a home automation project with a Raspberry Pi 3 and I need to run some python scripts when a txt file changes. Is there a way to watch if the file is changed? (Currently i use a python script which constantly opens the txt and checks if anything changed but its not efficient and it causes problems sometimes. Thanks in advance!

Answer 1

If you wanted to report changes to a single file in the local directory called foo.txt you can use watchdog (which is a skin over inotify, or equivalent) like this:

from time import sleep
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler

class Handler(FileSystemEventHandler):
    def on_modified(self, event):
        if event.src_path == "./foo.txt": # in this example, we only care about this one file
            print ("changed")

observer = Observer()
observer.schedule(Handler(), ".") # watch the local directory
observer.start()

try:
    while True:
        sleep(1)
except KeyboardInterrupt:
    observer.stop()

observer.join()