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# Glossary

dictionary

  A Python dictionary maps keys to values. Also known as “hashes”, or “associative arrays” in other programming languages. See the Python tutorial on dictionaries.

edge

  Edges are either two-tuples of nodes `(u, v)` or three tuples of nodes with an edge attribute dictionary `(u, v, dict)`.

ebunch

  An iterable container of edge tuples like a list, iterator, or file.

edge attribute

  Edges can have arbitrary Python objects assigned as attributes by using keyword/value pairs when adding an edge assigning to the `G.edges[u][v]` attribute dictionary for the specified edge u-v.

nbunch

  An nbunch is a single node, container of nodes or `None` (representing all nodes). It can be a list, set, graph, etc. To filter an nbunch so that only nodes actually in `G` appear, use `G.nbunch_iter(nbunch)`.

  If the nbunch is a container or iterable that is not itself a node in the graph, then it will be treated as an iterable of nodes, for instance, when nbunch is a string or a tuple:

      >>> import networkx as nx
      >>> G = nx.DiGraph()
      >>> G.add_edges_from([("b", "c"), ("a", "ab"), ("ab", "c")])
      >>> G.edges("ab")
      OutEdgeDataView([('ab', 'c')])

  Since “ab” is a node in G, it is treated as a single node:

      >>> G.edges("bc")
      OutEdgeDataView([('b', 'c')])

  Since “bc” is not a node in G, it is treated as an iterator:

      >>> G.edges(["bc"])
      OutEdgeDataView([])

  If “bc” is wrapped in a list, the list is the iterable and “bc” is treated as a single node. That is, if the nbunch is an iterable of iterables, the inner iterables will always be treated as nodes:

      >>> G.edges("de")
      OutEdgeDataView([])

  When nbunch is an iterator that is not itself a node and none of its elements are nodes, then the edge view suite of methods return an empty edge view.

node

  A node can be any hashable Python object except None.

node attribute

  Nodes can have arbitrary Python objects assigned as attributes by using keyword/value pairs when adding a node or assigning to the `G.nodes[n]` attribute dictionary for the specified node `n`.