old_contents: """
  from Thinking in Python, Bruce Eckel
  http://mindview.net/Books/TIPython
  
  Class support for "observer" pattern.
  
  The observer class is the base class
  for all smartcard package observers.
  
  Known subclasses:
          smartcard.ReaderObserver
  
  """
  
  from smartcard.Synchronization import *
  
  class Observer:
      def update(observable, arg):
          '''Called when the observed object is
          modified. You call an Observable object's
          notifyObservers method to notify all the
          object's observers of the change.'''
          pass
  
  class Observable(Synchronization):
      def __init__(self):
          self.obs = []
          self.changed = 0
          Synchronization.__init__(self)
  
      def addObserver(self, observer):
          if observer not in self.obs:
              self.obs.append(observer)
  
      def deleteObserver(self, observer):
          self.obs.remove(observer)
  
      def notifyObservers(self, arg=None):
          '''If 'changed' indicates that this object
          has changed, notify all its observers, then
          call clearChanged(). Each observer has its
          update() called with two arguments: this
          observable object and the generic 'arg'.'''
  
          self.mutex.acquire()
          try:
              if not self.changed:
                      return
              # Make a local copy in case of synchronous
              # additions of observers:
              localArray = self.obs[:]
              self.clearChanged()
          finally:
              self.mutex.release()
          # Update observers
          for observer in localArray:
              observer.update(self, arg)
  
      def deleteObservers(self):
              self.obs = []
      def setChanged(self):
              self.changed = 1
      def clearChanged(self):
              self.changed = 0
      def hasChanged(self):
              return self.changed
      def countObservers(self):
              return len(self.obs)
  
  synchronize(Observable,
      "addObserver deleteObserver deleteObservers " +
      "setChanged clearChanged hasChanged " +
      "countObservers")
  #:~
  
new_contents: """
  from Thinking in Python, Bruce Eckel
  http://mindview.net/Books/TIPython
  
  Class support for "observer" pattern.
  
  The observer class is the base class
  for all smartcard package observers.
  
  Known subclasses:
          smartcard.ReaderObserver
  
  """
  
  from smartcard.Synchronization import *
  
  
  class Observer:
  
      def update(observable, arg):
          '''Called when the observed object is
          modified. You call an Observable object's
          notifyObservers method to notify all the
          object's observers of the change.'''
          pass
  
  
  class Observable(Synchronization):
  
      def __init__(self):
          self.obs = []
          self.changed = 0
          Synchronization.__init__(self)
  
      def addObserver(self, observer):
          if observer not in self.obs:
              self.obs.append(observer)
  
      def deleteObserver(self, observer):
          self.obs.remove(observer)
  
      def notifyObservers(self, arg=None):
          '''If 'changed' indicates that this object
          has changed, notify all its observers, then
          call clearChanged(). Each observer has its
          update() called with two arguments: this
          observable object and the generic 'arg'.'''
  
          self.mutex.acquire()
          try:
              if not self.changed:
                      return
              # Make a local copy in case of synchronous
              # additions of observers:
              localArray = self.obs[:]
              self.clearChanged()
          finally:
              self.mutex.release()
          # Update observers
          for observer in localArray:
              observer.update(self, arg)
  
      def deleteObservers(self):
              self.obs = []
  
      def setChanged(self):
              self.changed = 1
  
      def clearChanged(self):
              self.changed = 0
  
      def hasChanged(self):
              return self.changed
  
      def countObservers(self):
              return len(self.obs)
  
  synchronize(Observable,
      "addObserver deleteObserver deleteObservers " +
      "setChanged clearChanged hasChanged " +
      "countObservers")
  #:~
  
subject: make pep8 happy