pi

from decimal import localcontext, Decimal


def pi(K, prec=100):
    """
    https://www.davidhbailey.com//
    """
    with localcontext() as ctx:
        ctx.prec = prec
        return sum(
            (Decimal(1) / Decimal(16 ** k)) * (
                +(Decimal(4) / (Decimal(8 * k) + Decimal(1)))
                -(Decimal(2) / (Decimal(8 * k) + Decimal(4)))
                -(Decimal(1) / (Decimal(8 * k) + Decimal(5)))
                -(Decimal(1) / (Decimal(8 * k) + Decimal(6)))
            )
            for k in range(K)
        )