{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "import random\n",
    "\n",
    "def sample(prob):\n",
    "    if random.random() < prob:\n",
    "        return True\n",
    "    else:\n",
    "        return False\n",
    "    \n",
    "random.seed(123)  # set the initial value of the pseudorandom number generator"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "def simulate_one_game():\n",
    "    points_for_you = 0\n",
    "    points_for_opponent = 0\n",
    "    current_server = 'you'\n",
    "\n",
    "    while points_for_you < 21 and points_for_opponent < 21:\n",
    "        if current_server == 'you': probability_of_winning = 0.6\n",
    "        else: probability_of_winning = 0.5\n",
    "\n",
    "        win = sample(probability_of_winning)   # did the server win?\n",
    "\n",
    "        if win:\n",
    "            if current_server == 'you': points_for_you += 1\n",
    "            elif current_server == 'opponent': points_for_opponent += 1\n",
    "\n",
    "        status = 'lost'\n",
    "        if win: status = 'won'\n",
    "        #print('%s served and %s; you=%d, opponent=%d' % (current_server, status, points_for_you, points_for_opponent ) )\n",
    "\n",
    "        if not win:\n",
    "            if current_server == 'you': current_server = 'opponent'\n",
    "            else: current_server = 'you'\n",
    "                \n",
    "    if points_for_you > points_for_opponent:\n",
    "        return True  # return True if you win\n",
    "    else:\n",
    "        return False # return False if you lose"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0.8248\n"
     ]
    }
   ],
   "source": [
    "times_won = 0\n",
    "total = 0\n",
    "\n",
    "for i in range(10000):\n",
    "    won = simulate_one_game()\n",
    "    if won: times_won += 1\n",
    "    total += 1\n",
    "    \n",
    "print(times_won / total)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.5.1"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}