import os

import time

from threading import Thread

class LogWatcher:

    def __init__(self):

        self.active = True

        self.t = None

        self.filename = None

        self.file_error = False

    def follow(self, thefile):

        thefile.seek(0, 2)  # Go to the end of the file

        while self.active:

            line = thefile.readline()

            if not line:

                time.sleep(0.1)  # Sleep briefly

                continue

            yield line

    def run(self):

        while not os.path.exists(self.filename):

            time.sleep(1)

            if not self.active:

                self.file_error = True

                return

        logfile = open(self.filename)

        print(logfile.read())

        loglines = self.follow(logfile)

        for line in loglines:

            print(line, end='')

    def start(self, filename):

        self.filename = filename

        self.t = Thread(target=self.run)

        self.t.start()

    def stop(self):

        self.active = False

        self.t.join()

        if not self.file_error:

            # delete log file

            os.remove(self.filename)

log_watcher = LogWatcher()