Does graph.nodes() maintain some ordering?

Question

With networkx2 does the .nodes() method guarantee some kind of consistent node ordering, or can we expect the ordering to change between multiple calls on the same graph?

Answer 1

Up to Python 3.6

The nodes are kept in a dictionary, and nodes() return a list of the dictionary keys. The order will be constant as long as you don't change anything in the graph nodes. Adding/removing nodes or edges might effect the order.

From Python 3.6:

In some Python implementations, like CPython, dictionary maintain the insertion order, which mean you can expect the print order, however not all of them

From Python 3.7:

Ordered dictionary is now language standard.

From the docs

def nodes(self): 
    """Return a copy of the graph nodes in a list.""" 
    return self.adj.keys()

networkx support Python 2.7, 3.4, 3.5, or 3.6, the behavior depends on your version.