Inconsistent Node ID Types Cause KeyError When Using Integer Node IDs

[hackl]

When constructing a graph from an edge list with integer node IDs, iterating over n.nodes and accessing dictionary-based methods such as degrees() results in a KeyError.

This is not working:

n = pp.Graph.from_edge_list([(0, 1), (1, 2), (2, 1)])
for v in n.nodes:
    print(n.degrees()[v])

Error:

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
Cell In[25], line 3
      1 n = pp.Graph.from_edge_list([(0, 1), (1, 2), (2, 1)])
      2 for v in n.nodes:
----> 3     print(n.degrees()[v])

KeyError: 0

Working example with string node IDs

n = pp.Graph.from_edge_list([('A', 'B'), ('B', 'C'), ('C', 'A')])
for v in n.nodes:
    print(n.degrees()[v])