如何使用Python监视文件而不是目录以进行更改? [英] How do I watch a file, not a directory for changes using Python?

问题描述

问题:如何观看文件使用Python进行更改?建议使用watchdog，但我发现它只能监视目录，而不能监视文件. watchdog-test.py 是看门狗的示例脚本:

The question: How do I watch a file for changes using Python? suggests using watchdog, but I found it was only able to watch a directory, not a file. watchdog-test.py is watchdog's sample script:

$ python watchdog-test.py ab_test_res.sh &
[1] 30628
fbt@fbt64:~/laike9m$ Traceback (most recent call last):
  File "watchdog-test.py", line 15, in <module>
    observer.start()
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/api.py", line 255, in start
    emitter.start()
  File "/usr/local/lib/python2.7/dist-packages/watchdog/utils/__init__.py", line 111, in start
    self.on_thread_start()
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/inotify.py", line 121, in on_thread_start
    self._inotify = InotifyBuffer(path, self.watch.is_recursive)
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/inotify_buffer.py", line 35, in __init__
    self._inotify = Inotify(path, recursive)
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/inotify_c.py", line 187, in __init__
    self._add_dir_watch(path, recursive, event_mask)
  File "/usr/local/lib/python2.7/dist-packages/watchdog/observers/inotify_c.py", line 363, in _add_dir_watch
    raise OSError('Path is not a directory')
OSError: Path is not a directory

那么最好的解决方案是什么?我正在使用Linux(Ubuntu 12.04).顺便说一句，我不想​​使用轮询.

So what's the best solution? I'm using Linux(Ubuntu 12.04). BTW I don't want to use polling.

推荐答案

您可以通过看门狗来监视文件，方法是观察文件所在的目录，并且仅响应影响文件的更改事件.这样的事情会帮你做到这一点:

You can watch a file with watchdog by watching the directory that the file is in and only responding to change events that effect your file. Something like this would do it for you:

from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler

class FileModifiedHandler(FileSystemEventHandler):

    def __init__(self, path, file_name, callback):
        self.file_name = file_name
        self.callback = callback

        # set observer to watch for changes in the directory
        self.observer = Observer()
        self.observer.schedule(self, path, recursive=False)
        self.observer.start()
        self.observer.join()

    def on_modified(self, event): 
        # only act on the change that we're looking for
        if not event.is_directory and event.src_path.endswith(self.file_name):
            self.observer.stop() # stop watching
            self.callback() # call callback


from sys import argv, exit

if __name__ == '__main__':

    if not len(argv) == 2:
        print("No file specified")
        exit(1)

    def callback():
        print("FILE WAS MODIFED")

    FileModifiedHandler('.', argv[1], callback)

我只能在Windows上对其进行测试，但是应该与操作系统无关.

I was only able to test this on windows, but it should be os agnostic.

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