dot-dsl: remove mutable default arguments (exercism#1838)

pranasziaukas · cmccandless · commit 42a039d7f161 · 2019-07-10T08:23:14.000-04:00
diff --git a/exercises/dot-dsl/dot_dsl.py b/exercises/dot-dsl/dot_dsl.py
@@ -2,7 +2,7 @@
 
 
 class Node(object):
-    def __init__(self, name, attrs={}):
+    def __init__(self, name, attrs):
         self.name = name
         self.attrs = attrs
 
@@ -11,7 +11,7 @@ def __eq__(self, other):
 
 
 class Edge(object):
-    def __init__(self, src, dst, attrs={}):
+    def __init__(self, src, dst, attrs):
         self.src = src
         self.dst = dst
         self.attrs = attrs
@@ -23,5 +23,5 @@ def __eq__(self, other):
 
 
 class Graph(object):
-    def __init__(self, data=[]):
+    def __init__(self, data=None):
         pass
diff --git a/exercises/dot-dsl/dot_dsl_test.py b/exercises/dot-dsl/dot_dsl_test.py
@@ -16,7 +16,7 @@ def test_graph_with_one_node(self):
             (NODE, "a", {})
         ])
 
-        self.assertEqual(g.nodes, [Node("a")])
+        self.assertEqual(g.nodes, [Node("a", {})])
         self.assertEqual(g.edges, [])
         self.assertEqual(g.attrs, {})
 
diff --git a/exercises/dot-dsl/example.py b/exercises/dot-dsl/example.py
@@ -2,7 +2,7 @@
 
 
 class Node(object):
-    def __init__(self, name, attrs={}):
+    def __init__(self, name, attrs):
         self.name = name
         self.attrs = attrs
 
@@ -11,7 +11,7 @@ def __eq__(self, other):
 
 
 class Edge(object):
-    def __init__(self, src, dst, attrs={}):
+    def __init__(self, src, dst, attrs):
         self.src = src
         self.dst = dst
         self.attrs = attrs
@@ -23,11 +23,14 @@ def __eq__(self, other):
 
 
 class Graph(object):
-    def __init__(self, data=[]):
+    def __init__(self, data=None):
         self.nodes = []
         self.edges = []
         self.attrs = {}
 
+        if data is None:
+            data = []
+
         if not isinstance(data, list):
             raise TypeError("Graph data malformed")
 
