dealing with empty graph

gmatch4py/graph.pyx

@@ -17,9 +17,13 @@ cdef class Graph:
         self.is_node_attr=(True if node_attr_key else False)
         self.is_edge_attr=(True if edge_attr_key else False)
         
-        if len(G) == 0:
-            return
+        if len(G) ==0:
+            self.nodes_list,self.nodes_attr_list,self.nodes_hash,self.nodes_weight,self.attr_nodes=[],[],[],[],[]
+            self.nodes_degree,self.nodes_degree_in,self.nodes_degree_out,self.nodes_degree_weighted,self.nodes_degree_in_weighted,self.nodes_degree_out_weighted=np.array([],dtype=np.long),np.array([],dtype=np.long),np.array([],dtype=np.long),np.array([],dtype=np.long),np.array([],dtype=np.long),np.array([],dtype=np.long)
+            self.nodes_idx,self.degree_per_attr,self.degree_per_attr_weighted={},{},{}
+            self.nodes_hash_set=set([])
 
+        else:
             a,b=list(zip(*list(G.nodes(data=True))))
             self.nodes_list,self.attr_nodes=list(a),list(b)
             if G.number_of_edges()>0:

setup.py

@@ -78,7 +78,7 @@ setup(
         ]
 )
 #Clean cpp and compiled file
-f=True
+f=False
 if f:
     if os.path.exists("build"):
         shutil.rmtree("build")