python判断输入的内容是否为一个数字(整数、负数)

def is_number(s):
    s = str(s)
    if s.count('.') == 1:#小数
        new_s = s.split('.')
        left_num = new_s[0]
        right_num = new_s[1]
        if right_num.isdigit():
            if left_num.isdigit():
               return True
            elif left_num.count('-') == 1 and left_num.startswith('-'):#负小数
                tmp_num = left_num.split('-')[-1]
                if tmp_num.isdigit():
                    return True
    elif s.count(".") == 0:#整数
        if s.isdigit():
            return True
        elif s.count('-') == 1 and s.startswith('-'):#负整数
            ss = s.split('-')[-1]
            if ss.isdigit():
                return True
    return False
    ```