判断浮点数

def is_float(s):
    s=str(s)
    if s.count(".")==1:
        s_list=s.split(".")
        left=s_list[0]
        right=s_list[1]
        if left.startswith("-") and left[1:].isdigit() and right.isdigit():
            return  True
        elif left.isdigit() and right.isdigit():
            return True
    return False
print(is_float(+8.0))