#------------------------------------------------------------------------------
#  stack.py
#  Definition of the Stack class.
#------------------------------------------------------------------------------

class Stack(object):
   """Stack class implementing a LIFO sequence type."""

   def __init__(self):
      """Initialize a Stack object."""
      self._list = []
   # end

   def __str__(self):
      """Return a string representation of self."""
      return str(self._list)
   # end

   def __repr__(self):
      """Return a detailed string representation of self."""
      return repr(self._list)
   # end

   def __len__(self):
      """Return the length of self."""
      return len(self._list)
   # end

   def isEmpty(self):
      """Return true iff self is empty, False otherwise."""
      return (len(self)==0)
   # end

   def push(self, x):
      """Add new item x to top of Stack."""
      self._list.append(x)
   # end

   def pop(self):
      """Delete and return top item, or Raise IndexError if empty."""
      if self.isEmpty():
         raise IndexError('pop() called on empty Stack')
      else:
         return self._list.pop()
      # end
   # end

   def peek(self):
      """Return (only) top item, or raise IndexError if empty."""
      if self.isEmpty():
         raise IndexError('peek() called on empty Stack')
      else:
         return self._list[-1]
      # end
   # end

# end 


#------------------------------------------------------------------------------
#  Test the Stack type
#------------------------------------------------------------------------------
def main():

   S = Stack()
   # print(S.pop())
   S.push('a')
   S.push('b')
   S.push('c')
   print(S.isEmpty())
   print(len(S))
   print(S.peek())
   print(S.pop())
   print(S.pop())
   print(S.pop())
   print(S.isEmpty())
   # S.pop()
   # S.peek()

# end

#------------------------------------------------------------------------------
if __name__=='__main__':

   main()

# end