Python version of Satoshi Nakamoto's blockchain formula originally written in C. Original function: https://bitcoin.org/bitcoin.pdf.

bitcoin.py

import math
import ast


def attacker_success_probability(q, z):
    p = (1 - q)
    lamb = (z * (q / p))
    some = 1
    k = 0
    while (k <= z):
        poisson = math.exp(-lamb)
        i = 1
        while (i <= k):
            poisson *= (lamb / i)
            i += 1
        some -= (poisson * (1 - math.pow(q / p, z - k)))
        k += 1
    attacker_success_probability.some = some

q = input("What is q? ")
q = ast.literal_eval(q)

z = input("What is z? ")
z = ast.literal_eval(z)

attacker_success_probability(q, z)

print('\nq={}\nz={}\tp={}'.format(q, z, attacker_success_probability.some))