Trouble getting Watchdog observer to stop/join (python)

Question

I'm using the watchdog python package to detect if a file has been downloaded (which I'm doing in selenium). This is the code I'm using and it successfully detects file creation, but my call to self.observer.stop() doesn't seem to work and the program stalls. Any thoughts?

class MyEventHandler(FileSystemEventHandler):
    def __init__(self, observer):
        self.observer = observer
    def on_created(self, event):
        print "file created"
        self.observer.stop()

def check_download(download_folder):
    file_location = download_folder
    print(download_folder)
    observer = Observer()
    event_handler = MyEventHandler(observer)
    observer.schedule(event_handler, file_location)
    observer.start()
    observer.join()
    return 0

Answer 1

Fixed with:

class MyEventHandler(FileSystemEventHandler):
    def __init__(self, observer):
        self.observer = observer

    def on_created(self, event):
        if not event.src_path.endswith(".pdf"):
            global check
            check = 1  # signal download complete


def initiate_download(PDF, download_folder):
    file_location = download_folder
    global check
    check = 0
    observer = Observer()
    event_handler = MyEventHandler(observer)
    observer.schedule(event_handler, file_location)
    observer.start()
    PDF.click()
    while check == 0:
        time.sleep(1)  # wait for download signal
    observer.stop()
    observer.join()
    return 0

Probably not a "proper" solution but it seemed to do the trick.