subject.py

class Subject(object):
  def __init__(self):
    self._observers = []

  def attach(self, observer):
    if not observer in self._observers:
      self._observers.append(observer)

  def detach(self, observer):
    try:
      self._observers.remove(observer)
    except ValueError:
      pass

  def notify(self, modifier=None):
    for observer in self._observers:
      if modifier != observer:
        observer.update(self)


# Example usage
class Data(Subject):
  def __init__(self, name=''):
    super(Data, self).__init__()
    self.name = name
    self._data = 0

  @property
  def data(self):
    return self._data

  @data.setter
  def data(self, value):
    self._data = value
    self.notify()


# class HexViewer(object):
#     def update(self, subject):
#         print('HexViewer: Subject %s has data 0x%x' % (subject.name, subject.data))
#
#
# class DecimalViewer(object):
#     def update(self, subject):
#         print('DecimalViewer: Subject %s has data %d' % (subject.name, subject.data))
#

def retrieve_count(l):
    return len(l)

# Example usage...
def main():

    data = DataStatistics('ThePirateBayScraper')
    view = MagnetAnalizedViewer()
    view0 = MagnetCounterViewer()

    data.attach(view0)
    data.attach(view)

    lista = ['a']
    data.analized_data = 1
    data.counter = len(lista)
    lista.append('ab')
    data.counter = len(lista)


    # data.counter = 1
    # data1 = Data('Data 1')
    # data2 = Data('Data 2')
    # view1 = DecimalViewer()
    # view2 = HexViewer()
    # data1.attach(view1)
    # data1.attach(view2)
    # data2.attach(view2)
    # data2.attach(view1)
    #
    # print("Setting Data 1 = 10")
    # data1.data = 10
    # print("Setting Data 2 = 15")
    # data2.data = 15
    # print("Setting Data 1 = 3")
    # data1.data = 3
    # print("Setting Data 2 = 5")
    # data2.data = 5
    # print("Detach HexViewer from data1 and data2.")
    # data1.detach(view2)
    # data2.detach(view2)
    # print("Setting Data 1 = 10")
    # data1.data = 10
    # print("Setting Data 2 = 15")
    # data2.data = 15

if __name__ == '__main__':
    main()