Handler

Handler, as the name suggest, handles the events that triggers by watcher. Basically in Handler you can decide what to do when an event happens, like a file is added to a directory.

There are 2 basic part in the Handler:

• catch the event

  • there are 4 event type: modified, created, deleted, moved

• do something with the event

Create a Handler

You need inherit from one the Watchdog Event Handler Classes

from watchdog.events import FileSystemEventHandler

Now you need to create the handler class.

Important

owl expects the class to called Handler

class Handler(FileSystemEventHandler):

Then decide which event to catch:

• on_any_event: Catch-all event handler
• on_created: Called when a file or directory is created
• on_modified: Called when a file or directory is created
• on_moved: Called when a file or directory is modified.
• on_deleted: Called when a file or a directory is moved or renamed.

In this example, we’re going to catch if the create and delete events

    def on_created(self, event):
        self.process_created_event(event)

    def on_deleted(self, event):
        self.process_delete_event(event)

Now this the fun part where you decide what to do with that event. Each event has 3 attributes which you can use to determine whether or not the you need to take action on this event:

• event_type: The type of the event as a string.
• is_directory: True if event was emitted for a directory; False otherwise.
• src_path: Source path of the file system object that triggered this event.

def process_created_event(self, event):
    created_path = event.src_path
    print "New file is created: {}".format(created_path)

def process_delete_event(self, event):
    deleted_path = event.src_path
    print "file is deleted: {}".format(deleted_path)

That’s the basic of how you can create a handler. There is a lot you can do once you start digging into the Watchdog. It’s fairly simple and powerful.

Here is the entire code:

from watchdog.events import FileSystemEventHandler

class Handler(FileSystemEventHandler):
    def on_created(self, event):
        self.process_created_event(event)

    def on_deleted(self, event):
        self.process_delete_event(event)

    def process_created_event(self, event):
        created_path = event.src_path
        print "New file is created: {}".format(created_path)

    def process_delete_event(self, event):
        deleted_path = event.src_path
        print "file is deleted: {}".format(deleted_path)