some algorithm...

unfair_coin.py

# http://sahandsaba.com/interview-question-groupon-probability.html
import random

def bernoulli_process(p):
    if p > 1.0 or p < 0.0:
        raise ValueError("p should be between 0.0 and 1.0.")
    while True:
        yield random.random() > p

def von_neumann_extractor(process):
    while True:
        x, y = next(process), next(process)
        if x != y: # only events: p * (1-p), (1-p) * p
            yield x # yield y is also fine.

def test(n):
    g = von_neumann_extractor(bernoulli_process(0.1)) # whatever from 0 - 1
    count = 0
    t = 0
    while count < n:
        count += 1
        if next(g):
            t += 1
    return t/count

test(10000)