Python，黑洞数问题代码

Question

o = 3  # input('请输入需要计算的黑洞数的位数：')

def jishuan(num):
    da = ''
    xiao = ''
    k = 0
    num1 = 10 ** int(o - 1)
    while num1 < 10 ** int(o):
        i = sorted(str(num1))
        a = sorted(str(num1), reverse=True)
        for c in i:
            da += str(c)
        for c in a:
            xiao += str(c)
        if int(da) - int(xiao) == int(num1):
            return num1
        else:
            num1 += 1

print(jishuan(o)) 

为什么输出一直为空

Answer 1

o = 3  # input('请输入需要计算的黑洞数的位数：')

def jishuan(num):
    k = 0
    num1 = 10 ** int(o - 1)
    while num1 < 10 ** int(o):
        i = sorted(str(num1), reverse=True)
        a = sorted(str(num1))
        da = ''
        xiao = ''
        for c in i:
            da += str(c)
        for c in a:
            xiao += str(c)
        if int(da) - int(xiao) == int(num1):
            return num1
        else:
            num1 += 1

print(jishuan(o))

应该是这样吧？结果是：495