Gallery: Improve plot_degree_sequence example (networkx#8601)

* More context for initial print.

* Remove unnecessary comments, more context for print.

* Replace bespoke hist with degree_histogram.

Author: rossbar

examples/graph/plot_degree_sequence.py

@@ -6,31 +6,27 @@
 Random graph from given degree sequence.
 """
 
+from pprint import pprint
 import matplotlib.pyplot as plt
 import networkx as nx
 
 # Specify seed for reproducibility
 seed = 668273
 
 z = [5, 3, 3, 3, 3, 2, 2, 2, 1, 1, 1]
-print(nx.is_graphical(z))
-
-print("Configuration model")
-G = nx.configuration_model(
-    z, seed=seed
-)  # configuration model, seed for reproducibility
-degree_sequence = [d for n, d in G.degree()]  # degree sequence
-print(f"Degree sequence {degree_sequence}")
-print("Degree histogram")
-hist = {}
-for d in degree_sequence:
-    if d in hist:
-        hist[d] += 1
-    else:
-        hist[d] = 1
-print("degree #nodes")
-for d in hist:
-    print(f"{d:4} {hist[d]:6}")
+print(f"Sequence {z} is a valid degree sequence: {nx.is_graphical(z)}")
+
+G = nx.configuration_model(z, seed=seed)
+degree_sequence = [d for _, d in G.degree()]
+
+# The degree sequence for the random graph computed using configuration_model
+# should match the degree sequence used to generate it
+print(f"Degree sequence of G identical to z: {degree_sequence == z}")
+
+print("\nDegree histogram")
+deg_hist = dict(enumerate(nx.degree_histogram(G)))
+print("degree: #nodes")
+pprint(deg_hist, width=10)
 
 pos = nx.spring_layout(G, seed=seed)  # Seed layout for reproducibility
 nx.draw(G, pos=pos)