def pi(N): ' 计算pi的值 ' # step 1: 创建一个奇数序列: 1, 3, 5, 7, 9, ... # step 2: 取该序列的前N项: 1, 3, 5, 7, 9, ..., 2*N-1. # step 3: 添加正负符号并用4除: 4/1, -4/3, 4/5, -4/7, 4/9, ... # step 4: 求和: odd_list = itertools.count(1, 2) # 创建一个奇数序列 limit_odd_list = itertools.takewhile(lambda x: 2 * N - 1 >= x, odd_list) # 截取N项的 def map_f(x): if not (x // 2) % 2: return 4 / x else: return -4 / x lst = map(map_f, limit_odd_list) result = sum(list(lst)) return result
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