π = 3.14
r = float(input('请输入圆的半径:'))
def area_of_circle(r):
if r <= 0:
return None
else:
return π*r**2
s = area_of_circle(r)
print("圆的面积为:",s)
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秦庆顺
π = 3.14
r = float(input('请输入圆的半径:'))
def area_of_circle(r):
if r <= 0:
return None
else:
return π*r**2
s = area_of_circle(r)
print("圆的面积为:",s)