编写程序找出范围内能被7整除不能被3整除的数

Question

Answer 1

def div7_not3(a, b):
    if a > b:
        return ''
    res = []
    for i in range(a, b):
        if i % 7 == 0 and i % 3 != 0:
            res.append(i)
    return ','.join(res)