python - I am attempting to print only a selected amount of Pi, it returns with an error of "Decimal has no attribute: __getitem__

Question

def pi():
    prompt=">>> "
    print "
WARNING: Pi may take some time to be calculated and may not always be correct beyond 100 digits."
    print "
Show 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__'

Answer 1

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