Short answer: f = open(... , 'w')
generates a FileCreatedEvent
, f.flush()
or f.close()
can generate a FileModifiedEvent
. So yes, creating a file often generates both FileCreatedEvent
and FileModifiedEvents
.
Whether or not you can safely ignore FileCreatedEvents depends on what you are trying to do. If you are interested in reacting whenever a file is created, then you need to handle FileCreatedEvents, and perhaps ignore FileModifiedEvents, since it is possible to generate FileModifiedEvents when modifying a file without generating FileCreatedEvents.
Play around with the canonical watchdog script (below) and all should be clearer.
Long answer: To see what is happening, run the canonical watchdog program straight from the docs:
import sys
import time
import logging
from watchdog.observers import Observer
from watchdog.events import LoggingEventHandler
if __name__ == "__main__":
logging.basicConfig(level=logging.INFO,
format='%(asctime)s - %(message)s',
datefmt='%Y-%m-%d %H:%M:%S')
path = sys.argv[1] if len(sys.argv) > 1 else '.'
event_handler = LoggingEventHandler()
observer = Observer()
observer.schedule(event_handler, path, recursive=True)
observer.start()
try:
while True:
time.sleep(1)
except KeyboardInterrupt:
observer.stop()
observer.join()
And from a terminal:
% mkdir ~/tmp
% cd ~/tmp
% script.py
Now in a Python interpreter when you open a file in w
mode:
In [126]: f = open('/home/unutbu/tmp/foobar', 'w')
The terminal prints
2014-02-05 16:29:34 - <FileCreatedEvent: src_path=/home/unutbu/tmp/foobar>
When you write to the file watchdog does not report any event:
In [127]: f.write('Hi')
But when you flush,
In [128]: f.flush()
it reports a FileModifiedEvent:
2014-02-05 16:29:55 - <FileModifiedEvent: src_path=/home/unutbu/tmp/foobar>
If you write more stuff to the file:
In [129]: f.write(' there')
similarly, a FileModifiedEvent is reported when you close the file, since more output is flushed to disk:
In [130]: f.close()
2014-02-05 16:30:12 - <FileModifiedEvent: src_path=/home/unutbu/tmp/foobar>