想问一下这怎么解啊啊

import math

r = int(input())
s = math.pi * r * r
print("%.2f" % s)

#!/usr/bin/python
# -*- coding: UTF-8 -*-
"""
@author: YangPC
@time:2021/06/21
@QQ:327844761
@微信公众号：ewbang
"""

from math import pi


def fun():
    r = int(input("请输入圆的半径:"))
    S = pi * r * r
    print("圆的面积为{:.2f}".format(S))


if __name__ == '__main__':
    fun()