python實現的鏈表棧

Stackclass EmptyStackException(Exception):    passclass Element:    def __init__(self, value, next):        self.value = value        self.next = nextclass Stack:    def __init__(self):        self.head = None        def push(self, element):        self.head = Element(element, self.head)        def pop(self):        if self.empty(): raise EmptyStackException        result = self.head.value        self.head = self.head.next        return result        def empty(self):        return self.head == Noneif __name__ == "__main__":        stack = Stack()    elements = ["first", "second", "third", "fourth"]    for e in elements:        stack.push(e)    result = []    while not stack.empty():        result.append(stack.pop())    assert result == ["fourth", "third", "second", "first"]