Update for those using networkx 2.x

The API has changed from v1.x to v2.x. networkx.degree no longer returns a dict but a DegreeView Object as per the documentation.

There is a guide for migrating from 1.x to 2.x here.

In this case it basically boils down to using dict(g.degree) instead of d = nx.degree(g).

The updated code looks like this:

import networkx as nx
import matplotlib.pyplot as plt

g = nx.Graph()
g.add_edges_from([(1,2), (2,3), (2,4), (3,4)])

d = dict(g.degree)

nx.draw(g, nodelist=d.keys(), node_size=[v * 100 for v in d.values()])
plt.show()

nx.degree(p) returns a dict while the node_size keywod argument needs a scalar or an array of sizes. You can use the dict nx.degree returns like this:

import networkx as nx
import matplotlib.pyplot as plt

g = nx.Graph()
g.add_edges_from([(1,2), (2,3), (2,4), (3,4)])

d = nx.degree(g)

nx.draw(g, nodelist=d.keys(), node_size=[v * 100 for v in d.values()])
plt.show()