Python练习：10进制转2进制

题目：把输入的任意十进制数转换成2进制并输出。

class stackDT:
    '''构造栈的数据类型'''
    def __init__(self):
        self.items = []
    def isempty(self):
        return self.items == []
    def push(self, item):
        self.items.append(item)
    def pop(self):
        return self.items.pop()
    def peek(self):
        return self.items[-1]
    def size(self):
        return len(self.items)

def decimaltobinary(iptnum):
    optnum = ''
    iptnum_2 = stackDT()
    while iptnum > 0:
        (iptnum, i) = divmod(iptnum, 2)
        iptnum_2.push(str(i))
    while not iptnum_2.isempty():
        optnum += str(iptnum_2.pop())
    return optnum

binarynum = decimaltobinary(eval(input()))
print(binarynum)

题目来自中国大学MOOC中北京大学陈斌副教授的MOOC：《数据结构与算法Python版》