item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done Exception as e: print('Exception: %s %s' % (e, url)) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.

decorator like tornado.gen.coroutine or asyncio.coroutine [https://docs.python.org/3.5/library/asyncio-task.html#asyncio.coroutine]), not all coroutines are compatible with each other. There is a coroutine callbacks instead of Future, wrap the call in a Task. This will add the callback argument for you and return a Future which you can yield: @gen.coroutine def call_task(): # Note that there are no parens on on some_function. # This will be translated by Task into # some_function(other_args, callback=callback) yield gen.Task(some_function, other_args) Calling blocking functions The simplest way

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done Exception as e: print("Exception: %s %s" % (e, url)) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done print("Exception: %s %s" % (e, url)) dead.add(url) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.

call in a Task. This will add the callback argument for you and return a Future which you can yield: 4.1. User’s guide 13 Tornado Documentation, Release 4.5.3 @gen.coroutine def call_task(): # Note there are no parens on some_function. # This will be translated by Task into # some_function(other_args, callback=callback) yield gen.Task(some_function, other_args) Calling blocking functions The simplest item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done print("Exception: %s %s" % (e, url)) dead.add(url) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done try: await fetch_url(url) except Exception as e: print('Exception: %s %s' % (e, url)) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty. workers

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done print("Exception: %s %s" % (e, url)) dead.add(url) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done print("Exception: %s %s" % (e, url)) dead.add(url) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.

item. A Queue maintains a count of unfinished tasks, which begins at zero. put increments the count; task_done decrements it. In the web-spider example here, the queue begins containing only base_url. When calls task_done to decrement the counter once. Eventually, a worker fetches a page whose URLs have all been seen before, and there is also no work left in the queue. Thus that worker’s call to task_done print("Exception: %s %s" % (e, url)) dead.add(url) finally: q.task_done() await q.put(base_url) # Start workers, then wait for the work queue to be empty.