def pygraphviz_layout(G, prog='neato', root=None, args=''):
 try:
  import pygraphviz
 except ImportError:
  raise ImportError('requires pygraphviz ', 'http://pygraphviz.github.io/')
 if (root is not None):
  args += ('-Groot=%s' % root)
 A = to_agraph(G)
 A.layout(prog=prog, args=args)
 node_pos = {}
 for n in G:
  node = pygraphviz.Node(A, n)
  try:
   (xx, yy) = node.attr['pos'].split(',')
   node_pos[n] = (float(xx), float(yy))
  except:
   print ('no position for node', n)
   node_pos[n] = (0.0, 0.0)
 return node_pos

def pygraphviz_layout ( G , prog = 'neato' , root = None , args = '' ) : try : import pygraphviz except ImportError : raise ImportError ( 'requires pygraphviz ' , 'http://pygraphviz.github.io/' ) if ( root is not None ) : args += ( '-Groot=%s' % root ) A = to_agraph ( G ) A . layout ( prog = prog , args = args ) node_pos = { } for n in G : node = pygraphviz . Node ( A , n ) try : ( xx , yy ) = node . attr [ 'pos' ] . split ( ',' ) node_pos [ n ] = ( float ( xx ) , float ( yy ) ) except : print ( 'no position for node' , n ) node_pos [ n ] = ( 0.0 , 0.0 ) return node_pos
create node positions for g using graphviz .