[addresses] Topological sort of address component dependencies so they get checked/removed in order

scripts/geodata/graph/topsort.py

@@ -0,0 +1,32 @@
+
+def topsort(graph):
+    '''
+    Topological sort for a dependency graph, e.g.
+
+    Usage:
+
+    >>> graph = {
+            'a': ['b'],
+            'b': ['d'],
+            'c': ['d', 'a'],
+            'd': [],
+        }
+    >>> topsort(graph)
+
+    Returns: ['d', 'b', 'a', 'c']
+
+    '''
+    todos = set(graph.keys())
+    seen = set()
+    result = []
+    while todos:
+        for key in todos:
+            deps = graph[key]
+            if len([d for d in deps if d in seen]) == len(deps):
+                break
+        else:
+            raise Exception('Cycle: {}'.format(todos))
+        todos.remove(key)
+        result.append(key)
+        seen.add(key)
+    return result