Example of file change monitoring watchdog in python

This article mainly introduces the file change monitoring example (watchdog) in python. The editor thinks it is quite good. Now I will share it with you and give it as a reference. Let’s follow the editor and take a look.

There are two main libraries for file monitoring in python, one is pyinotify (https://github.com/seb-m/pyinotify/wiki) and the other is watchdog ( http://pythonhosted.org/watchdog/). pyinotify relies on the Linux platform's inotify, which encapsulates events on different platforms. Because I mainly use it on the Windows platform, I will focus on watchdog below (it is recommended that you read the watchdog implementation source code, which will help you deeply understand the principles).

watchdog uses different methods for file detection on different platforms. The following comments were found in init.py:

|Inotify| Linux 2.6.13+ ``inotify(7)`` based observer
|FSEvents| Mac OS X FSEvents based observer
|Kqueue| Mac OS X and BSD with kqueue(2) ``kqueue(2)`` based observer
|WinApi|(ReadDirectoryChangesW) MS Windows Windows API-based observer
|Polling| Any fallback implementation

The sample code is given as follows:

##

from watchdog.observers import Observer
from watchdog.events import *
import time

class FileEventHandler(FileSystemEventHandler):
def __init__(self):
FileSystemEventHandler.__init__(self)

def on_moved(self, event):
if event.is_directory:
print("directory moved from {0} to {1}".format(event.src_path,event.dest_path))
else:
print("file moved from {0} to {1}".format(event.src_path,event.dest_path))

def on_created(self, event):
if event.is_directory:
print("directory created:{0}".format(event.src_path))
else:
print("file created:{0}".format(event.src_path))

def on_deleted(self, event):
if event.is_directory:
print("directory deleted:{0}".format(event.src_path))
else:
print("file deleted:{0}".format(event.src_path))

def on_modified(self, event):
if event.is_directory:
print("directory modified:{0}".format(event.src_path))
else:
print("file modified:{0}".format(event.src_path))

if __name__ == "__main__":
observer = Observer()
event_handler = FileEventHandler()
observer.schedule(event_handler,"d:/dcm",True)
observer.start()
try:
while True:
time.sleep(1)
except KeyboardInterrupt:
observer.stop()
observer.join()

watchdog main Use the observer model (nonsense, you can tell from the variable naming). There are three main roles: observer, event_handler, and monitored folder. The three are originally independent. They are connected mainly through the observer.schedule function, which means that the observer continuously detects and calls the platform-dependent code to detect changes in the monitoring folder. When changes are found, the event_handler is notified for processing. Finally, I highly recommend readers to read the source code of watchdog when they have time. It is easy to understand and has a good structure.

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