Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/networkx/algorithms/components/attracting.py

@@ -0,0 +1,111 @@
+"""Attracting components."""
+import networkx as nx
+from networkx.utils.decorators import not_implemented_for
+
+__all__ = [
+    "number_attracting_components",
+    "attracting_components",
+    "is_attracting_component",
+]
+
+
+@not_implemented_for("undirected")
+def attracting_components(G):
+    """Generates the attracting components in `G`.
+
+    An attracting component in a directed graph `G` is a strongly connected
+    component with the property that a random walker on the graph will never
+    leave the component, once it enters the component.
+
+    The nodes in attracting components can also be thought of as recurrent
+    nodes.  If a random walker enters the attractor containing the node, then
+    the node will be visited infinitely often.
+
+    To obtain induced subgraphs on each component use:
+    ``(G.subgraph(c).copy() for c in attracting_components(G))``
+
+    Parameters
+    ----------
+    G : DiGraph, MultiDiGraph
+        The graph to be analyzed.
+
+    Returns
+    -------
+    attractors : generator of sets
+        A generator of sets of nodes, one for each attracting component of G.
+
+    Raises
+    ------
+    NetworkXNotImplemented
+        If the input graph is undirected.
+
+    See Also
+    --------
+    number_attracting_components
+    is_attracting_component
+
+    """
+    scc = list(nx.strongly_connected_components(G))
+    cG = nx.condensation(G, scc)
+    for n in cG:
+        if cG.out_degree(n) == 0:
+            yield scc[n]
+
+
+@not_implemented_for("undirected")
+def number_attracting_components(G):
+    """Returns the number of attracting components in `G`.
+
+    Parameters
+    ----------
+    G : DiGraph, MultiDiGraph
+        The graph to be analyzed.
+
+    Returns
+    -------
+    n : int
+        The number of attracting components in G.
+
+    Raises
+    ------
+    NetworkXNotImplemented
+        If the input graph is undirected.
+
+    See Also
+    --------
+    attracting_components
+    is_attracting_component
+
+    """
+    return sum(1 for ac in attracting_components(G))
+
+
+@not_implemented_for("undirected")
+def is_attracting_component(G):
+    """Returns True if `G` consists of a single attracting component.
+
+    Parameters
+    ----------
+    G : DiGraph, MultiDiGraph
+        The graph to be analyzed.
+
+    Returns
+    -------
+    attracting : bool
+        True if `G` has a single attracting component. Otherwise, False.
+
+    Raises
+    ------
+    NetworkXNotImplemented
+        If the input graph is undirected.
+
+    See Also
+    --------
+    attracting_components
+    number_attracting_components
+
+    """
+    ac = list(attracting_components(G))
+    if len(ac) == 1:
+        return len(ac[0]) == len(G)
+    return False