import networkx as nx
import matplotlib.pyplot as plt

G = nx.MultiDiGraph()

G.add_edges_from([
  ('t1', 'c1'),
  ('t1', 'c2'),
  ('c1', 'c2'),
  ('c2', 'c1'),
  ('p2', 'c1'),
  ('c2', 'p2')
])

attrs = {'c1':{'key':100},
         'c2':{'key':50},
         't1':{'key':15},
         'p2':{'key':30}}
nx.set_node_attributes(G, attrs)

node_sizes = [a['key']*30 for n, a in G.nodes(data=True)]

# drawing ...
pos = {key: [i*3, 0] for key, i in zip(attrs, range(len(attrs)))}
print(pos)
nx.draw(G, pos, with_labels=True,
        cmap=plt.get_cmap('jet'),
        node_size=node_sizes,
        arrows=True, arrowsize=40)