Area of basic exercise circle ※

import math


r = int(input())

s = r*r*math.pi

print('%.7f'%s)

I don't know if I can 　ｉｍｐｏｒｔ　ｍａｔｈ　

So an awkward afternoon ...

subject ： Enter the radius , The area of the output circle , It is required to keep after the decimal point 7 position

PI=3.14159265358979323

r = int(input())
kk = r*r*PI
print('kk is :',kk)
s = str(r*r*PI)



for i in range(len(s)):
    if s[i]=='.':
        w = s[0:i+8]
        w = float(w)
        print(w)
      
        if int(s[i+8])>=5:
            print(' Finally confirm ： ',w)
            w = w + 0.0000001
        print(w)
        
            

 

Finally, it is confirmed that there is no problem , Add one 0.0000001 Just ok 了

however , Add a 0.000000100000005

I remember , The teacher said before , Floating point numbers are stored approximately in a computer . This explains the phenomenon .

Can you beat me up ？

false AC

PI=3.14159265358979323

r = int(input())

s = str(r*r*PI)

s = list(s)

for i in range(len(s)):
    if s[i]=='.':
        if int(s[i+8]) >=5:    
            s[i+7]=chr(ord(s[i+7])+1)

        for j in range(i+8):
            print(s[j],end='')
        break

Guess the cause of error ： Retain ４ Decimal place ～　　０．２３９９５　＋０．０００１　

actual 　＝　０．２４００ 

Program －－－＞０.２３９０　　（ Only on the th day after the decimal point ４ Bit plus １）

(￣ε(#￣)

really ～　AC

PI=3.14159265358979323

r = int(input())

s = str(r*r*PI)
ss = r*r*PI

for i in range(len(s)):
    if s[i]=='.':
        if int(s[i+8])>=5:
            ss += 0.0000001
        sss = str(ss)
        for j in range(i+8):
            print(sss[j],end='')