Q:

Drawing nodes of multigraph in fixed position

What i Have : a multigraph with four nodes and four edge. Each node has a position specified (the nodes form a squadre structure)
What i want: drawing the multigraph with nodes posistions.
PROBLEM: Positions are ignored in the final layout.
This is my code :
import networkx as nx
import pydot
from my_lib import *
graph= nx.MultiGraph()

#add 4 nodes in the vertexs of a square. X and Y are the coordinates
graph.add_node(1,x=10,y=10)
graph.add_node(2,x=10,y=20)
graph.add_node(3,x=20,y=10)
graph.add_node(4,x=20,y=20)
graph.add_edge(1,2)
graph.add_edge(2,3)
graph.add_edge(3,4)
graph.add_edge(4,1)

#transform the multigraph in pydot for draw it
graphDot=nx.to_pydot(graph)

#change some attribute for the draw, like shape of nodes and the position of nodes 
for node in graphDot.get_nodes():

    node.set_shape('circle')
    #getAttrDot is a function that returns the value of attribute passed
    pos_string='\''+ get_attrDot(node,'x')+','+get_attrDot(node,'y')+'!\''
    print 'coordinate: ' + pos_string  #the pos_string printed is correct form: 'x,y!'
    node.set('pos',pos_string)

graphDot.write_png('test_position.png')

Here the result of this code. 
The image 'test_position.png' is :[1]: http://imgur.com/dDj3xFl
As you can see, the node positions are ignored.
Can you help me please?
Thanks!
EDIT SOLVED: The suggest of Aric solved my problem. THANKS!!!

A:

You can set the attributes before you convert the graph to a Pydot object:
import networkx as nx                                                                                     
graph= nx.MultiGraph()                                                                                    

#add 4 nodes in the vertexs of a square. X and Y are the coordinates                                      
graph.add_node(1,x=100,y=100)                                                                             
graph.add_node(2,x=100,y=200)                                                                             
graph.add_node(3,x=200,y=100)                                                                             
graph.add_node(4,x=200,y=200)                                                                             
graph.add_edge(1,2)                                                                                       
graph.add_edge(2,3)                                                                                       
graph.add_edge(3,4)                                                                                       
graph.add_edge(4,1)                                                                                       
                                                                                                         # assign positions                                                                                        
for n in graph:                                                                                           
    graph.node[n]['pos'] = '"%d,%d"'%(graph.node[n]['x'], graph.node[n]['y'])                             
p = nx.to_pydot(graph)                                                                                    
print p.to_string()                                                                                       
p.write('foo.dot')                                                                                        
# run neato -n2 -Tpng foo.dot >foo.png  

The output is:
graph G {
1 [y=100, x=100, pos="100,100"];
2 [y=200, x=100, pos="100,200"];
3 [y=100, x=200, pos="200,100"];
4 [y=200, x=200, pos="200,200"];
1 -- 2  [key=0];
1 -- 4  [key=0];
2 -- 3  [key=0];
3 -- 4  [key=0];
}

Run 
neato -n2 -Tpng foo.dot >foo.png 
(the -n2 keeps your node positions)

