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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.misc,sci.electronics.design
Subject: Re: Totally OT: Colliding blocks that compute pi
Date: Fri, 21 Mar 2025 06:16:44 -0000 (UTC)
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On Thu, 20 Mar 2025 13:15:38 +0000, SH wrote:

> How I wish I could calculate pi

Your computer can do it!

    import decimal

    Dec = decimal.Decimal
    decctx = decimal.getcontext()
    decctx.prec = 64

    def decimal_pi():
        with decimal.localcontext() as decctx :
            decctx.prec += 2    # extra digits for intermediate steps
            t = Dec(3)      # substitute 3.0 for regular floats
            lasts, s, n, na, d, da = 0, 3, 1, 0, 0, 24
            nr_steps = 0
            while s != lasts :
                nr_steps += 1
                lasts = s
                n, na = n + na, na + 8
                d, da = d + da, da + 32
                t = t * n / d
                s += t
            #end while
        #end with
        print("nr_steps = %d" % nr_steps)
        return +s               # unary plus applies the new precision
    #end decimal_pi

    print(decimal_pi())

output:

    nr_steps = 104
    3.141592653589793238462643383279502884197169399375105820974944592

Taken from a presentation I did here
<https://github.com/HamPUG/meetings/blob/master/2022/2022-11-14/ldo/Continued%20Fractions.ipynb>.

I tried continued fractions, but found them a waste of time.