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chess_masters.py

#!/usr/bin/env python

"""
An example of the XDiGraph class with multiple 
edges (multiedges=True)).

The function chess_pgn_graph reads a collection of chess 
matches stored in the specified PGN file 
(PGN ="Portable Game Notation")
Here the (compressed) default file ---
 chess_masters_WCC.pgn.bz2 ---
contains all 685 World Chess Championship matches
from 1886 - 1985.
(data from http://chessproblem.my-free-games.com/chess/games/Download-PGN.php)

The chess_pgn_graph() function returns an XDiGraph 
with multiple edges but no self-loops. Each node is 
the last name of a chess master. Each edge is directed 
from white to black and contains selected game info.

The key statement in chess_pgn_graph below is
    G.add_edge(white, black, game_info)
where game_info is a dict describing each game.

"""
#    Copyright (C) 2006 by 
#    Aric Hagberg <hagberg@lanl.gov>
#    Dan Schult <dschult@colgate.edu>
#    Pieter Swart <swart@lanl.gov>
#    Distributed under the terms of the GNU Lesser General Public License
#    http://www.gnu.org/copyleft/lesser.html

from networkx import *

# tag names specifying what game info should be 
# stored in the dict on each digraph edge
game_details=[
              "Event", 
              "Date", 
              "Result", 
              "ECO",
              "Site"
             ]

def chess_pgn_graph(pgn_file="chess_masters_WCC.pgn.bz2"):
    """Read chess games in pgn format in pgn_file.
    
    Filenames ending in .gz or .bz2 will be uncompressed.
    
    Return the XDiGraph of players connected by a chess game.
    Edges contain game data in a dict.

    """
    try:# use networkx.io._get_fh to uncompress
        # pgn file if required
        datafile=io._get_fh(pgn_file,mode='rb')
    except IOError:
        print "Could not read file %s."%(pgn_file)
        raise
    G=XDiGraph(multiedges=True)
    game_info={}
    for line in datafile.read().splitlines():
        # check for tag pairs
        if len(line)>0 and line[0]=='[':
           line=line[1:-1] # remove extra quotes
         tag = line.split()[0]
           value=line[len(tag)+2:-1]
         if tag=='White':
              white=value.split(',')[0]
         elif tag=='Black':
              black=value.split(',')[0]
           elif tag in game_details:
            game_info[tag]=value
        # empty line after tag set indicates 
        # we finished reading game info
        elif len(line)==0:
           if len(game_info)>0: 
                 G.add_edge(white, black, game_info)
             game_info={}
    return G


if __name__ == '__main__':
    from networkx import *
    try:
      import pylab as P
    except:
      print """pylab not found: 
               see https://networkx.lanl.gov/Drawing.html for info"""
      raise 

    G=chess_pgn_graph()
    ngames=G.number_of_edges()
    nplayers=G.number_of_nodes()

    print "Loaded %d chess games between %d players\n"\
                   % (ngames,nplayers)

    # identify connected components
    # of the undirected version
    Gcc=connected_component_subgraphs(G.to_undirected())
    if len(Gcc)>1:
        print "Note the disconnected component consisting of:"
        print Gcc[1].nodes()    

    # find all games with B97 opening (as described in ECO)
    openings=set([game_info['ECO'] for (white,black,game_info) in G.edges()])
    print "\nFrom a total of %d different openings,"%len(openings)
    print 'the following games used the Sicilian opening'
    print 'with the Najdorff 7...Qb6 "Poisoned Pawn" variation.\n'

    for (white,black,game_info) in G.edges():
      if game_info['ECO']=='B97':
         print white,"vs",black
           for k,v in game_info.items():
               print "   ",k,": ",v
           print "\n"


    try: # drawing
        P.figure(figsize=(8,8))
        # make new undirected graph H without multi-edges
        H=G.copy()
        H.ban_multiedges()
        H=H.to_undirected()

        # edge width is proportional number of games played
        edgewidth=[]
        for (u,v,d) in H.edges():
            edgewidth.append(len(G.get_edge(u,v)))

        # node size is proportional to number of games won
        wins=dict.fromkeys(G.nodes(),0.0)
        for (u,v,d) in G.edges():
            r=d['Result'].split('-')
            if r[0]=='1':
                wins[u]+=1.0
            elif r[0]=='1/2':
                wins[u]+=0.5
                wins[v]+=0.5
            else:
                wins[v]+=1.0

        pos=graphviz_layout(H)


      draw_networkx_edges(H,pos,
                      alpha=0.3,
                      width=edgewidth,
                      edge_color='m'
                      )
      draw_networkx_nodes(H,pos,
                      node_size=[wins[v]*35 for v in H],
                      node_color='r',
                      alpha=0.4,
                      )
      draw_networkx_edges(H,pos,
                         alpha=0.4,
                         node_size=0,
                         width=1,
                         edge_color='k'
                         )
        draw_networkx_labels(H,pos,
                             fontsize=14)
        font = {'fontname'   : 'Helvetica',
        'color'      : 'k',
        'fontweight' : 'bold',
        'fontsize'   : 14}
      P.title("World Chess Championship Games: 1886 - 1985", font)

        # change font and write text (using data coordinates)
        font = {'fontname'   : 'Helvetica',
        'color'      : 'r',
        'fontweight' : 'bold',
        'fontsize'   : 14}
        xmin, xmax, ymin, ymax = P.axis()
        dx = xmax - xmin
        dy = ymax - ymin
        x = 0.1*dx + xmin
        y = 0.9*dy + ymin
        P.text(x, y, "edge width = # games played")
        y = 0.85*dy + ymin
        P.text(x, y,  "node size = # games won")

      # turn off x and y axes labels in pylab
      P.xticks([])
      P.yticks([])

      P.savefig("chess_masters_graph.png",dpi=75)
        print "Wrote chess_masters_graph.png"
        P.show() # display
    except:
      print "Unable to draw: problem with graphviz or pylab"

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