python类堆栈

class zhan:
    def __init__(self):
        self.s=['1','2']
    def top(self):
        if self.s:
            return self.s[-1]
        return False
    def yazhan(self,name):
        self.s.extend(name)
        return True
    def tanzhan(self):
        if self.s:
            res=self.s.pop()
            return res
        return False
    def changdu(self):
        return len(self.s)
    def chakan(self):
        return self.s
    def seek(self,name):
        if name not in self.s:
            return False
        return self.s.index(name)

A=zhan()
# print(A.changdu(),A.yazhan('3'),A.yazhan('3'),A.tanzhan(),\
#       A.chakan())
print(A.seek(''))