Destructive Stack Iteration

Question

This is my Stack implementation.

class Stack:
    def __init__(self):
        self.head = None
        self.size = 0

    def push(self, item):
        node          


        

Answer 1

The problem is that you do not make a difference between the iterable Stack itself and the iterator that __iter__ should return. __next__ should be called on said iterator, not on the Stack itself.

I propose the following solution:

class StackIterator:
    def __init__(self, stack):
        self.head = stack.head

    def __iter__(self):
        return self

    def __next__(self):
        if not self.head:
            raise StopIteration

        current = self.head
        self.head = self.head.next

        return current.val

Get rid of __next__ in Stack and adjust __iter__ to:

def __iter__(self):
    return StackIterator(self)

Demo:

>>> stack = Stack()
>>> stack.push(12)
>>> stack.push(13)
>>> stack.push(9)
>>> 
>>> for x in stack:
...     print(x)
... 
9
13
12
>>> stack.peek()
9