我试图只打印选定数量的 Pi，它返回错误“十进制没有属性:__getitem__ [英] I am attempting to print only a selected amount of Pi, it returns with an error of "Decimal has no attribute: __getitem__

问题描述

def pi():
    prompt=">>> "
    print "\nWARNING: Pi may take some time to be calculated and may not always be correct beyond 100 digits."
    print "\nShow Pi to what digit?"
    n=raw_input(prompt)
    from decimal import Decimal, localcontext
    with localcontext() as ctx:
        ctx.prec = 10000
        pi = Decimal(0) 
        for k in range(350): 
            pi += (Decimal(4)/(Decimal(8)*k+1) - Decimal(2)/(Decimal(8)*k+4) - Decimal(1)/(Decimal(8)*k+5) - Decimal(1)/(Decimal(8)*k+6)) / Decimal(16)**k
    print pi[:int(n)]
pi()




Traceback (most recent call last):
  File "/Users/patrickcook/Documents/Pi", line 13, in <module>
    pi()
  File "/Users/patrickcook/Documents/Pi", line 12, in pi
    print pi[:int(n)]
TypeError: 'Decimal' object has no attribute '__getitem__'

推荐答案

当 pi 是一个 Decimal 时，您正试图将它视为一个数组.我认为您正在寻找 quantize:https://docs.python.org/2/library/decimal.html

You are trying to treat pi as an array, when it is a Decimal. I think you are looking for quantize:https://docs.python.org/2/library/decimal.html

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