Calculation for the Chess SE question: http://chess.stackexchange.com/questions/8561/top-player-with-the-lowest-drawing-rate

draw_rates.py

#!/usr/bin/python
from __future__ import division
from collections import Counter
import pgn
import operator
import os
from matplotlib import pyplot as plt
from matplotlib import rcParams
rcParams.update({'figure.autolayout': True})
import numpy as np
PGN_DIR = 'pgns'
PGN_SUBDIRS = {'men', 'women'}

def calculate_draw_rates(directory):
	pgn_files = os.listdir(os.path.join(PGN_DIR, directory))
	draw_rates = dict()
	for fname in pgn_files:
		pgn_file = open(os.path.join(PGN_DIR, directory, fname), 'r')
		player_name = fname.split('.')[0]
		pgn_text = pgn_file.read()
		pgn_file.close()
		games = pgn.loads(pgn_text)
		results = [game.result for game in games]
		num_games = len(results)
		counts = Counter(results)
		num_draws = counts['1/2-1/2']
		draw_rate = round(num_draws / num_games, 3)
		draw_rates[player_name] = draw_rate
	return draw_rates

def plot_draw_rates(draw_rates, directory):
	sorted_results = sorted(draw_rates.items(), key=operator.itemgetter(1))
	player_names = [item[0] for item in sorted_results]
	draws = [item[1] for item in sorted_results]
	average_draw_rate = np.mean(draws)
	plt.bar(range(0, len(player_names)), draws)
	plt.axhline(y=average_draw_rate, color='red', linewidth='4', label='Average')
	plt.xticks(range(0, len(player_names)), player_names, rotation=90)
	plt.title("Draw rates " + directory, size=18)
	plt.xlabel("Player name", size=14)
	plt.ylabel("Draw rate", size=14)
	plt.grid(True)
	plt.legend(loc=2)
	plt.savefig("draw_rates_"+directory+".png")
	plt.clf()
	plt.close()

for dir_entry in PGN_SUBDIRS:
	data = calculate_draw_rates(dir_entry)
	plot_draw_rates(data, dir_entry)