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桂兴牛2号

#1 Created at ... [Delete] [Delete and Lock User]

import itertools

def pi(N):

#创建自然数列，取2n项，再提取奇数n项
natuals = itertools.count(1)
ns=itertools.takewhile(lambda x : x<=2*N,natuals)
ns_odd=list(filter(lambda x : x%2==1,ns))
sum=0
#分别除4或-4并求和
for i in range(0, len(ns_odd)):
    if i % 2==0:
        sum+=4/ns_odd[i]
    else:
        sum+=(-4/ns_odd[i])
return sum

测试:

print(pi(10)) print(pi(100)) print(pi(1000)) print(pi(10000)) assert 3.04 < pi(10) < 3.05 assert 3.13 < pi(100) < 3.14 assert 3.140 < pi(1000) < 3.141 assert 3.1414 < pi(10000) < 3.1415 print('ok')

用户5548570427

#2 Created at ... [Delete] [Delete and Lock User]

def pi(N): ' 计算pi的值 '

# step 1: 创建一个奇数序列: 1, 3, 5, 7, 9, ...
odd=itertools.count(1,2)
# step 2: 取该序列的前N项: 1, 3, 5, 7, 9, ..., 2*N-1.
n_odd=list(itertools.takewhile(lambda x:x<=2*N-1,odd))
# step 3: 添加正负符号并用4除: 4/1, -4/3, 4/5, -4/7, 4/9, ...
for i in range(len(n_odd)):
    sum=0
    if i%2==0:
        sum=sum+4/n_odd[i]
    else:
        sum=sum-4/n_odd[i]
# step 4: 求和:
return sum

我这样写为什么是错的啊

ZJahon

#3 Created at ... [Delete] [Delete and Lock User]

sum=0要放在循环外，不然每次循环都是0

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