PokerHandSoln.py

"""This module contains code from
Think Python by Allen B. Downey
http://thinkpython.com

Copyright 2012 Allen B. Downey
License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html

"""

import sys

from Card import *


class Hist(dict):
    """A map from each item (x) to its frequency."""

    def __init__(self, seq=[]):
        "Creates a new histogram starting with the items in seq."
        for x in seq:
            self.count(x)

    def count(self, x, f=1):
        "Increments the counter associated with item x."
        self[x] = self.get(x, 0) + f
        if self[x] == 0:
            del self[x]


class PokerHand(Hand):
    """Represents a poker hand."""

    all_labels = ['straightflush', 'fourkind', 'fullhouse', 'flush',
                  'straight', 'threekind', 'twopair', 'pair', 'highcard']

    def make_histograms(self):
        """Computes histograms for suits and hands.

        Creates attributes:

          suits: a histogram of the suits in the hand.
          ranks: a histogram of the ranks.
          sets: a sorted list of the rank sets in the hand.
        """
        self.suits = Hist()
        self.ranks = Hist()
        
        for c in self.cards:
            self.suits.count(c.suit)
            self.ranks.count(c.rank)

        self.sets = self.ranks.values()
        self.sets.sort(reverse=True)
 
    def has_highcard(self):
        """Returns True if this hand has a high card."""
        return len(self.cards)
        
    def check_sets(self, *t):
        """Checks whether self.sets contains sets that are
        at least as big as the requirements in t.

        t: list of int
        """
        for need, have in zip(t, self.sets):
            if need > have: return False
        return True

    def has_pair(self):
        """Checks whether this hand has a pair."""
        return self.check_sets(2)
        
    def has_twopair(self):
        """Checks whether this hand has two pair."""
        return self.check_sets(2, 2)
        
    def has_threekind(self):
        """Checks whether this hand has three of a kind."""
        return self.check_sets(3)
        
    def has_fourkind(self):
        """Checks whether this hand has four of a kind."""
        return self.check_sets(4)

    def has_fullhouse(self):
        """Checks whether this hand has a full house."""
        return self.check_sets(3, 2)

    def has_flush(self):
        """Checks whether this hand has a flush."""
        for val in self.suits.values():
            if val >= 5:
                return True
	return False

    def has_straight(self):
        """Checks whether this hand has a straight."""
        # make a copy of the rank histogram before we mess with it
        ranks = self.ranks.copy()
        ranks[14] = ranks.get(1, 0)

        # see if we have 5 in a row
        return self.in_a_row(ranks, 5)

    def in_a_row(self, ranks, n):
        """Checks whether the histogram has n ranks in a row.

        hist: map from rank to frequency
        n: number we need to get to
        """
        count = 0
        for i in range(1, 15):
            if ranks.get(i, 0):
                count += 1
                if count == 5: return True
            else:
                count = 0
        return False
    
    def has_straightflush(self):
        """Checks whether this hand has a straight flush.

        Clumsy algorithm.
        """
        # make a set of the (rank, suit) pairs we have
        s = set()
        for c in self.cards:
            s.add((c.rank, c.suit))
            if c.rank == 1:
                s.add((14, c.suit))

        # iterate through the suits and ranks and see if we
        # get to 5 in a row
        for suit in range(4):
            count = 0
            for rank in range(1, 15):
                if (rank, suit) in s:
                    count += 1
                    if count == 5: return True
                else:
                    count = 0
        return False
                
    def has_straightflush(self):
        """Checks whether this hand has a straight flush.

        Better algorithm (in the sense of being more demonstrably
        correct).
        """
        # partition the hand by suit and check each
        # sub-hand for a straight
        d = {}
        for c in self.cards:
            d.setdefault(c.suit, PokerHand()).add_card(c)

        # see if any of the partitioned hands has a straight
        for hand in d.values():
            if len(hand.cards) < 5:
                continue            
            hand.make_histograms()
            if hand.has_straight():
                return True
        return False


    def classify(self):
        """Classifies this hand.

        Creates attributes:
          labels:
        """
        self.make_histograms()

        self.labels = []
        for label in PokerHand.all_labels:
            f = getattr(self, 'has_' + label)
            if f():
                self.labels.append(label)


class PokerDeck(Deck):
    """Represents a deck of cards that can deal poker hands."""

    def deal_hands(deck, num_cards=5, num_hands=10):
        hands = []
        for i in range(num_hands):        
            hand = PokerHand()
            deck.move_cards(hand, num_cards)
            hand.classify()
            hands.append(hand)
        return hands


def main(*args):
    # the label histogram: map from label to number of occurances
    lhist = Hist()

    # loop n times, dealing 7 hands per iteration, 7 cards each
    n = 10000
    for i in range(n):
        if i%1000 == 0:
            print i
            
        deck = PokerDeck()
        deck.shuffle()

        hands = deck.deal_hands(7, 7)
        for hand in hands:
            for label in hand.labels:
                lhist.count(label)
            
    # print the results
    total = 7.0 * n
    print total, 'hands dealt:'

    for label in PokerHand.all_labels:
        freq = lhist.get(label, 0)
        if freq == 0: 
            continue
        p = total / freq
        print '%s happens one time in %.2f' % (label, p)

        
if __name__ == '__main__':
    main(*sys.argv)