之前学的生成器

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

import itertools

def pi(N):

odd_gen = [2 * i + 1 for i in range(999999)]

odd_list = []

for n in range(N):

if n % 2:

odd_list.append(4/-odd_gen[n])

else:

odd_list.append(4/odd_gen[n])

return sum(odd_list)

# 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')

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

itertools

def pi(n):

odds = itertools.takewhile(lambda x: x < 2 * n, itertools.count(1, 2))

fac = itertools.cycle([1, -1])

sum = 0

for i in odds:

sum += 4 * next(fac) / i

return sum