monitor logcat for a string match

logcat_monitor.py

#! /usr/bin/env python

# from http://stackoverflow.com/questions/11524586/accessing-logcat-from-android-via-python
import Queue
import subprocess
import threading
import datetime

class AsynchronousFileReader(threading.Thread):
    '''
    Helper class to implement asynchronous reading of a file
    in a separate thread. Pushes read lines on a queue to
    be consumed in another thread.
    '''

    def __init__(self, fd, queue):
        assert isinstance(queue, Queue.Queue)
        assert callable(fd.readline)
        threading.Thread.__init__(self)
        self._fd = fd
        self._queue = queue

    def run(self):
        '''The body of the tread: read lines and put them on the queue.'''
        for line in iter(self._fd.readline, ''):
            self._queue.put(line)

    def eof(self):
        '''Check whether there is no more content to expect.'''
        return not self.is_alive() and self._queue.empty()

def substring_matches_line(line):
    target_substring = "Foo"
    return target_substring in line

# You'll need to add any command line arguments here.
process = subprocess.Popen(['adb', 'logcat'], stdout=subprocess.PIPE)

# Launch the asynchronous readers of the process' stdout.
stdout_queue = Queue.Queue()
stdout_reader = AsynchronousFileReader(process.stdout, stdout_queue)
stdout_reader.start()

# Check the queues if we received some output (until there is nothing more to get).
still_looking = True
try:
  while still_looking and not stdout_reader.eof():
	    while not stdout_queue.empty():
	        line = stdout_queue.get()
	        if substring_matches_line(line):
	            print "Hoorah, I found it! " + str(datetime.datetime.now())
	            print line
	            still_looking = False
	            break
finally:
	process.kill()