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[python]watchdog 库使用

打算写一个文件监控的python程序
了解了一下watchdog这个库
打算学习一下=。=

概述

watchdog用来监控指定目录/文件的变化,如添加删除文件或目录、修改文件内容、重命名文件或目录等,每种变化都会产生一个事件,且有一个特定的事件类与之对应,然后再通过事件处理类来处理对应的事件,怎么样处理事件完全可以自定义,只需继承事件处理类的基类并重写对应实例方法。

使用例子

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()

-w708

使用方法

  • Create an instance of the watchdog.observers.Observer thread class.
  • Implement a subclass of watchdog.events.FileSystemEventHandler (or as in our case, we will use the built-in watchdog.events.LoggingEventHandler, which already does).
  • Schedule monitoring a few paths with the observer instance attaching the event handler.
  • Start the observer thread and wait for it generate events without blocking our main thread.。

上面两个是events和observer
介绍一下

events

主要的内容都在events这个文件里面
包含了所有的可监听的事件
看一下例子的LoggingEventHandler

class LoggingEventHandler(FileSystemEventHandler):
    """Logs all the events captured."""

    def on_moved(self, event):
        super(LoggingEventHandler, self).on_moved(event)

        what = 'directory' if event.is_directory else 'file'
        logging.info("Moved %s: from %s to %s", what, event.src_path,
                     event.dest_path)

    def on_created(self, event):
        super(LoggingEventHandler, self).on_created(event)

        what = 'directory' if event.is_directory else 'file'
        logging.info("Created %s: %s", what, event.src_path)

    def on_deleted(self, event):
        super(LoggingEventHandler, self).on_deleted(event)

        what = 'directory' if event.is_directory else 'file'
        logging.info("Deleted %s: %s", what, event.src_path)

    def on_modified(self, event):
        super(LoggingEventHandler, self).on_modified(event)

        what = 'directory' if event.is_directory else 'file'
        logging.info("Modified %s: %s", what, event.src_path)

watchdog.events.FileSystemEventHandler()
事件处理器的基类,用于处理事件,用户需继承该类,并在子类中重写对应方法。

类实例方法如下:
– self.dispatch(event)
接收到一个事件后,通过该方法来决定该event由下面哪个方法处理

    def dispatch(self, event):
        """Dispatches events to the appropriate methods.

        :param event:
            The event object representing the file system event.
        :type event:
            :class:`FileSystemEvent`
        """
        self.on_any_event(event)
        _method_map = {
            EVENT_TYPE_MODIFIED: self.on_modified,
            EVENT_TYPE_MOVED: self.on_moved,
            EVENT_TYPE_CREATED: self.on_created,
            EVENT_TYPE_DELETED: self.on_deleted,
        }
        event_type = event.event_type
        _method_map[event_type](event)
  • self.on_any_event(event)
    任何事件发生都会首先执行该方法,该方法默认为空,dispatch()方法会先执行该方法,然后再把event分派给其他方法处理

  • self.on_moved(event)
    Called when a file or a directory is moved or renamed,也就是处理DirMovedEvent和FileMovedEvent事件,子类需重写该方法

  • self.on_created(event)
    Called when a file or directory is created,也就是处理DirCreatedEvent和FileCreatedEvent事件,子类需重写该方法

  • self.on_deleted(event)
    Called when a file or directory is deleted,也就是处理DirDeletedEvent和FileDeletedEvent事件,子类需重写该方法

  • self.on_modified(event)
    Called when a file or directory is modified,也就是处理DirModifiedEvent和FileModifiedEvent事件,子类需重写该方法

observer

watchdog.observers.Observer(timeout=1)

该类实现了监控文件变化,触发对应的事件类,然后调用关联的事件处理类来处理事件。该类其实是threading.Thread的子类,通过observer.start()使之运行在一个线程中,不会阻塞主进程运行,然后可以调用observer.stop()来停止该线程
实例属性及方法:
observer.schedule(event_handler, path, recursive=False)
监控指定路径path,该路径触发任何事件都会调用event_handler来处理,如果path是目录,则recursive=True则会递归监控该目录的所有变化。每一次调用schedule()对一个路径进行监控处理就叫做一个watch,schedule()方法会返回这个watch,接着可以对这个watch做其他操作,如为该watch增加多个event处理器等
注:内部由一个字典handlers来保存所有watch,watch的值是一个集合,包含对应此watch的所有event handler:


handlers = { watch1: set(event_handler1, event_handler2), watch2: set(event_handler), }
  • observer.add_handler_for_watch(event_handler, watch)
    添加一个新的事件处理器到watch中,watch是ObservedWatch()类或其子类的实例

  • observer.remove_handler_for_watch(event_handler, watch)
    从watch中移除一个事件处理器

  • observer.unschedule(watch)
    移除一个watch及这个watch上的所有事件处理器

  • observer.unschedule_all()
    移除所有watch及关联的事件处理器

  • observer.on_thread_stop()
    等同于observer.unschedule_all()

  • observer.stop()
    调用该方法来停止observer线程

参考资料

https://pythonhosted.org/watchdog/
https://blog.csdn.net/chdhust/article/details/50514391

后记

差不多懂了=。=可以写一个文件监控了=。=只要继承一下FileSystemEventHandler然后重写一下函数就行了
github: https://github.com/woadsl1234/FileMonitor

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