adding alternative constructors for directed and undirected graphs

Author: Roman Lishtaba

README.md

@@ -503,10 +503,10 @@ Any DAG has at least one topological ordering, and algorithms are known for cons
 
 ```python
 
-from py_algorithms.graph import new_graph, topological_sort_f1
+from py_algorithms.graph import new_directed_graph, topological_sort_f1
 
 
-dag = new_graph(directed=True)
+dag = new_directed_graph()
 a = dag.insert_vertex('A')
 b = dag.insert_vertex('B')
 c = dag.insert_vertex('C')

py_algorithms/graph/__init__.py

@@ -1,8 +1,9 @@
 __all__ = [
     'Graph',
     'Vertex',
-    'new_graph'
-    'topological_sort_f1'
+    'directed_graph'
+    'new_undirected_graph'
+    'new_topological_sort_f1'
 ]
 
 from typing import List, Callable
@@ -12,8 +13,12 @@
 from .topological_sort import TopologicalSort
 
 
-def new_graph(directed: bool = False) -> Graph:
-    return Graph(directed)
+def new_directed_graph() -> Graph:
+    return Graph(directed=True)
+
+
+def new_undirected_graph() -> Graph:
+    return Graph(directed=False)
 
 
 def new_topological_sort() -> Callable[[Graph], List[Vertex]]:

tests/py_algorithms/graph/adt/graph_test.py

@@ -1,9 +1,9 @@
-from py_algorithms.graph import new_graph
+from py_algorithms.graph import new_undirected_graph
 
 
 class TestGraphApi:
     def test_graph_constructor(self):
-        g = new_graph()
+        g = new_undirected_graph()
         v1 = g.insert_vertex("A")
         v2 = g.insert_vertex("B")
         v3 = g.insert_vertex("C")

tests/py_algorithms/graph/topological_sort_test.py

@@ -1,9 +1,9 @@
-from py_algorithms.graph import new_graph, topological_sort_f1
+from py_algorithms.graph import new_directed_graph, topological_sort_f1
 
 
 class TestTopologicalSort:
     def test_topological_sort(self):
-        dag = new_graph(directed=True)
+        dag = new_directed_graph()
         a = dag.insert_vertex('A')
         b = dag.insert_vertex('B')
         c = dag.insert_vertex('C')