Decorator Recipe: Custom Event Binding
======================================

Step 0
------

.. sourcecode:: python

    from threading import Thread
    import time
        
    class Downloader(object):
        def __init__(self, url_list):
            self.url_list = url_list
            self.done_callback = None

        def start_downloads(self):
            thread = Thread(target=self.download_all)
            thread.start()
        
        def download_all(self):
            count = 0
            start_time = time.time()
            
            for url in self.url_list:
                print 'Downloading', url
                time.sleep(0.3)
                count += 1

            end_time = time.time()
            if self.done_callback:
                self.done_callback(count, end_time - start_time)

    if __name__ == '__main__':
        url_list = xrange(1, 13)
        downloader = Downloader(url_list)

        def ondone(num_downloaded, time_elapsed):
            print "Fetched", num_downloaded, "files in", time_elapsed, "seconds"

        downloader.done_callback = ondone

        downloader.start_downloads()

        print 'Waiting for the result...'

Expected result::

    Waiting for the result...
    Downloading 1
    Downloading 2
    Downloading 3
    Downloading 4
    Downloading 5
    Downloading 6
    Downloading 7
    Downloading 8
    Downloading 9
    Downloading 10
    Downloading 11
    Downloading 12
    Fetched 12 files in 3.60899996758 seconds
    
Solution: `downloader0.py <solutions/downloader0.py>`_

`Go to next step <step1.html>`_