CODEWITHSUNDEEP
multithreadingpython-2.7filesystemwatcher
wishi
wishi

Reputation: 7387

Is an infinite loop the best solution to process based on file changes in a directory

I am programming a tool which adds files to a processing chain. I want to monitor a specific known directory every 10s, compare, and send the results to my already existing functions.

I wrote a short class:

class Watchdog(Thread):

    def __init__(self, path):
        """ Constructor """
        self.watch_folder = path
        self.verbose = True

        pass

    def run(self):
        """
        we check every 10s
        """
        sleep_duration = 10
        before = dict ([(f, None) for f in os.listdir (self.watch_folder)])

        while True:
            time.sleep(sleep_duration)
            after = dict ([(f, None) for f in os.listdir (self.watch_folder)])

            added_files = [f for f in after if not f in before]
            removed_files = [f for f in before if not f in after]

            if added_files and self.verbose:
                print "Added: ", ", ".join (added_files)
            if removed_files and self.verbose:
                print "Removed: ", ", ".join (removed_files)


            before = after
        return added_files

I understand that due to the endless loop I cannot easily return the data. Especially because the rest of the program is imperative 

if __name__ == '__main__':
    functionA()

    do_smth()

    # added_files is returned from the Thread and ideally changing. 
    if added_files >= n:
        for file in added_files:
            # happycode goes here, but how do I know about the change each time?

In particular: can I simply (without using queue models or anything crazily complex) return from the thread? I would like to start the processing functions once the Thread can report a change (so this is my Observer).

I wonder if there is a simpler way to return from the endless loop so that the rest of the program can remain imperative.

Upvotes: 1

Views: 103

Answers (1)

Srinivas Varma
Srinivas Varma

Reputation: 56

  1. Here's a good article on what you're looking for (and lucky for you, in python)

http://timgolden.me.uk/python/win32_how_do_i/watch_directory_for_changes.html

  1. Alternatively, I would use the 'find -mtime n' linux command in python, if this is for a linux/linux like OS

EDIT: I know 1 and 2, don't answer your question on infinite loop, but are alternatives. Also,

  1. http://linux.die.net/man/1/dnotify might be an alternative as well

Hope this helps

Upvotes: 3

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