five-minute solution for express puzzle from https://fivethirtyeight.com/features/is-your-friend-full-of-it/

freethrows.py

#!/usr/bin/env python3

import argparse
import sys
import random

def simulate(accuracy, goal):
  i, streak = 0, 0
  while streak < goal:
    i += 1
    if random.random() < accuracy:
      streak += 1
    else:
      streak = 0
  return i

def avg(vals):
  total, num = 0, 0
  for v in vals:
    total += v
    num += 1
  return total / float(num)

def main():
  parser = argparse.ArgumentParser()
  parser.add_argument('--trials', type=int, default=10000)
  parser.add_argument('--goal', type=int, default=17)
  parser.add_argument('--accuracy', type=float, default=0.7)
  args = parser.parse_args()
  print(avg(simulate(args.accuracy, args.goal) for i in range(args.trials)))

if __name__ == "__main__":
  sys.exit(main())