python中檔案變化監控-watchdog
阿新 • • 發佈:2019-01-01
在python中檔案監控主要有兩個庫,一個是pyinotify ( https://github.com/seb-m/pyinotify/wiki ),一個是watchdog(http://pythonhosted.org/watchdog/)。pyinotify依賴於Linux平臺的inotify,後者則對不同平臺的的事件都進行了封裝。因為我主要用於Windows平臺,所以下面著重介紹watchdog(推薦大家閱讀一下watchdog實現原始碼,有利於深刻的理解其中的原理)。
watchdog在不同的平臺使用不同的方法進行檔案檢測。在init.py中發現瞭如下注釋:
|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
給出示例程式碼如下:
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主要採用觀察者模型(廢話,從變數命名就可以看出來)。主要有三個角色:observer,event_handler,被監控的資料夾。三者原本是獨立的,主要通過observer.schedule函式將三者串起來,意思為observer不斷檢測呼叫平臺依賴程式碼對監控資料夾進行變動檢測,當發現改變時,通知event_handler處理。最後特別推薦讀者有時間可以閱讀一下watchdog的原始碼,寫的易懂而且架構很好。