用Python编写的小数类型判断习题

def is_float(s):
    s=str(s)
    if  s.count('.')==1:
        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('-'):
               tmp_num=left_num.split('-')[-1]
               if tmp_num.isdigit():
                   return True

    return False

print(is_float('-9.6'))  #调用函数