使用python实现栈和队列

 1 class stack():
 2     def __init__(self):
 3         self.stack = []
 4     def empty(self):
 5         return self.stack==[]
 6     def push(self,data):
 7         self.stack.append(data)
 8     def pop(self):
 9         if self.empty():
10             return None;
11         else:
12             return self.stack.pop(-1)
13     def top(self):
14         if self.empty():
15             return None
16         else:
17             return self.stack[-1]
18     def length(self):
19         return len(self.stack)

class queue():
    def __init__(self):
        self.queue = []
    def empty(self):
        return self.queue == []
    def enqueue(self,data):
        self.queue.append(data)
    def dequeue(self):
        if self.empty():
            return None
        else:
            return self.queue.pop(0)
    
    #返回头信息和队列长度可以不实现
    def head(self):
        if self.empty():
            return None
        else:
            return self.queue[0]
    def length(self):
        return len(self.queue)