Make networkx and scipy optional even for nxapi (#30)

Author: eriknw

graphblas_algorithms/interface.py

@@ -1,4 +1,3 @@
-import networkx as nx
 import pytest
 
 from . import nxapi
@@ -70,6 +69,8 @@ class Dispatcher:
 
     @staticmethod
     def convert(graph, weight=None):
+        import networkx as nx
+
         from .classes import DiGraph, Graph, MultiDiGraph, MultiGraph
 
         if isinstance(graph, nx.MultiDiGraph):

graphblas_algorithms/nxapi/centrality/eigenvector.py

@@ -1,22 +1,22 @@
-import networkx as nx
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 from graphblas_algorithms.utils import not_implemented_for
 
+from ..exception import NetworkXError, NetworkXPointlessConcept, PowerIterationFailedConvergence
+
 __all__ = ["eigenvector_centrality"]
 
 
 @not_implemented_for("multigraph")
 def eigenvector_centrality(G, max_iter=100, tol=1.0e-6, nstart=None, weight=None):
     G = to_graph(G, weight=weight, dtype=float)
     if len(G) == 0:
-        raise nx.NetworkXPointlessConcept("cannot compute centrality for the null graph")
+        raise NetworkXPointlessConcept("cannot compute centrality for the null graph")
     x = G.dict_to_vector(nstart, dtype=float, name="nstart")
     try:
         result = algorithms.eigenvector_centrality(G, max_iter=max_iter, tol=tol, nstart=x)
     except algorithms.exceptions.ConvergenceFailure as e:
-        raise nx.PowerIterationFailedConvergence(*e.args) from e
+        raise PowerIterationFailedConvergence(*e.args) from e
     except algorithms.exceptions.GraphBlasAlgorithmException as e:
-        raise nx.NetworkXError(*e.args) from e
+        raise NetworkXError(*e.args) from e
     return G.vector_to_nodemap(result)

graphblas_algorithms/nxapi/centrality/katz.py

@@ -1,9 +1,9 @@
-import networkx as nx
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 from graphblas_algorithms.utils import not_implemented_for
 
+from ..exception import NetworkXError, PowerIterationFailedConvergence
+
 __all__ = ["katz_centrality"]
 
 
@@ -28,13 +28,13 @@ def katz_centrality(
         try:
             b = G.dict_to_vector(beta, dtype=float, name="beta")
         except (TypeError, ValueError, AttributeError) as e:
-            raise nx.NetworkXError(*e.args) from e
+            raise NetworkXError(*e.args) from e
     try:
         result = algorithms.katz_centrality(
             G, alpha=alpha, beta=b, max_iter=max_iter, tol=tol, nstart=x, normalized=normalized
         )
     except algorithms.exceptions.ConvergenceFailure as e:
-        raise nx.PowerIterationFailedConvergence(*e.args) from e
+        raise PowerIterationFailedConvergence(*e.args) from e
     except algorithms.exceptions.GraphBlasAlgorithmException as e:
-        raise nx.NetworkXError(*e.args) from e
+        raise NetworkXError(*e.args) from e
     return G.vector_to_nodemap(result)

graphblas_algorithms/nxapi/dag.py

@@ -1,8 +1,8 @@
-from networkx import NetworkXError
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 
+from .exception import NetworkXError
+
 __all__ = ["descendants", "ancestors"]
 
 

graphblas_algorithms/nxapi/exception.py

@@ -0,0 +1,35 @@
+try:
+    import networkx as nx
+except ImportError:
+
+    class NetworkXError(Exception):
+        pass
+
+    class NetworkXPointlessConcept(Exception):
+        pass
+
+    class NodeNotFound(Exception):
+        pass
+
+    class PowerIterationFailedConvergence(Exception):
+        pass
+
+else:
+    from networkx import (
+        NetworkXError,
+        NetworkXPointlessConcept,
+        NodeNotFound,
+        PowerIterationFailedConvergence,
+    )
+try:
+    import scipy as sp
+except ImportError:
+
+    class ArpackNoConvergence(Exception):
+        def __init__(self, msg, eigenvalues, eigenvectors):
+            super().__init__(msg)
+            self.eigenvalues = eigenvalues
+            self.eigenvectors = eigenvectors
+
+else:
+    from scipy.sparse.linalg import ArpackNoConvergence

graphblas_algorithms/nxapi/link_analysis/hits_alg.py

@@ -1,8 +1,8 @@
-from scipy.sparse.linalg import ArpackNoConvergence
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 
+from ..exception import ArpackNoConvergence
+
 __all__ = ["hits"]
 
 

graphblas_algorithms/nxapi/link_analysis/pagerank_alg.py

@@ -1,8 +1,8 @@
-import networkx as nx
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 
+from ..exception import PowerIterationFailedConvergence
+
 _all = ["pagerank"]
 
 
@@ -41,4 +41,4 @@ def pagerank(
         )
         return G.vector_to_nodemap(result, fillvalue=0.0)
     except algorithms.exceptions.ConvergenceFailure as e:
-        raise nx.PowerIterationFailedConvergence(*e.args) from e
+        raise PowerIterationFailedConvergence(*e.args) from e

graphblas_algorithms/nxapi/reciprocity.py

@@ -1,9 +1,9 @@
-from networkx import NetworkXError
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_directed_graph
 from graphblas_algorithms.utils import not_implemented_for
 
+from .exception import NetworkXError
+
 __all__ = ["reciprocity", "overall_reciprocity"]
 
 

graphblas_algorithms/nxapi/shortest_paths/generic.py

@@ -1,8 +1,8 @@
-from networkx import NodeNotFound
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 
+from ..exception import NodeNotFound
+
 __all__ = ["has_path"]
 
 

graphblas_algorithms/nxapi/smetric.py

@@ -1,8 +1,8 @@
-from networkx import NetworkXError
-
 from graphblas_algorithms import algorithms
 from graphblas_algorithms.classes.digraph import to_graph
 
+from .exception import NetworkXError
+
 __all__ = ["s_metric"]