Problem:Implement a queue class in Python: It should support 3 APIs:
queue.top(): prints current element at front of queue
queue.pop(): takes out an element from front of queue
queue.add(): adds a new element at end of queue
class Queue: def __init__(self): """initialise a Queue class""" self.items = [] self.index = len(self.items) - 1 def top(self): """returns the current element at front of queue""" if self.items: return self.items[0] else: raise Exception("Empty Queue") def pop(self): """takes out an element from front of queue""" if self.items: self.items.pop(0) else : raise Exception("Empty Queue") def add(self , item): """adds a new element at the end of queue""" self.items.append(item) def __str__(self): """returns the string representation""" return str(self.items) def __iter__(self): """iterates over the sequence""" return self def __next__(self): """returns the next value in sequence""" if self.index == 0 : raise StopIteration self.index -= 1 return self.items[self.index] queue_1 = Queue() queue_1.add(12) queue_1.add(11) queue_1.add(55) queue_1.add(66) queue_1.add(56) queue_1.add(43) queue_1.add(33) queue_1.add(88) queue_1.add(56) queue_1.add(34) iter(queue_1) for i in queue_1: print i print queue_1 print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() print queue_1.top() queue_1.pop() The code works as intended and executes the 3 APIs specified in the problem . But it gives “”TypeError: instance has no next() method”” when i try to use next method to iterate over the values in queue. What am i missing in defining the next method?
