Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/networkx/algorithms/isolate.py

@@ -0,0 +1,103 @@
+"""
+Functions for identifying isolate (degree zero) nodes.
+"""
+
+__all__ = ["is_isolate", "isolates", "number_of_isolates"]
+
+
+def is_isolate(G, n):
+    """Determines whether a node is an isolate.
+
+    An *isolate* is a node with no neighbors (that is, with degree
+    zero). For directed graphs, this means no in-neighbors and no
+    out-neighbors.
+
+    Parameters
+    ----------
+    G : NetworkX graph
+
+    n : node
+        A node in `G`.
+
+    Returns
+    -------
+    is_isolate : bool
+       True if and only if `n` has no neighbors.
+
+    Examples
+    --------
+    >>> G = nx.Graph()
+    >>> G.add_edge(1, 2)
+    >>> G.add_node(3)
+    >>> nx.is_isolate(G, 2)
+    False
+    >>> nx.is_isolate(G, 3)
+    True
+    """
+    return G.degree(n) == 0
+
+
+def isolates(G):
+    """Iterator over isolates in the graph.
+
+    An *isolate* is a node with no neighbors (that is, with degree
+    zero). For directed graphs, this means no in-neighbors and no
+    out-neighbors.
+
+    Parameters
+    ----------
+    G : NetworkX graph
+
+    Returns
+    -------
+    iterator
+        An iterator over the isolates of `G`.
+
+    Examples
+    --------
+    To get a list of all isolates of a graph, use the :class:`list`
+    constructor::
+
+        >>> G = nx.Graph()
+        >>> G.add_edge(1, 2)
+        >>> G.add_node(3)
+        >>> list(nx.isolates(G))
+        [3]
+
+    To remove all isolates in the graph, first create a list of the
+    isolates, then use :meth:`Graph.remove_nodes_from`::
+
+        >>> G.remove_nodes_from(list(nx.isolates(G)))
+        >>> list(G)
+        [1, 2]
+
+    For digraphs, isolates have zero in-degree and zero out_degre::
+
+        >>> G = nx.DiGraph([(0, 1), (1, 2)])
+        >>> G.add_node(3)
+        >>> list(nx.isolates(G))
+        [3]
+
+    """
+    return (n for n, d in G.degree() if d == 0)
+
+
+def number_of_isolates(G):
+    """Returns the number of isolates in the graph.
+
+    An *isolate* is a node with no neighbors (that is, with degree
+    zero). For directed graphs, this means no in-neighbors and no
+    out-neighbors.
+
+    Parameters
+    ----------
+    G : NetworkX graph
+
+    Returns
+    -------
+    int
+        The number of degree zero nodes in the graph `G`.
+
+    """
+    # TODO This can be parallelized.
+    return sum(1 for v in isolates(G))