一行代码打印:1-1/3+1/5-1/7...的前n项的和的4倍 , 值就是pi的近似值
>>> Pi = lambda n: 4*sum([(-1)**(i+1)/(2*i-1) for i in range(1,n+1)]) >>> Pi(10000) 3.1414926535900345 >>> Pi(100000) 3.1415826535897198 >>> Pi(1000000) 3.1415916535897743