bpo-17005: Move topological sort functionality to its own module (GH-20558)
The topological sort functionality that was introduced initially in the
functools module has been moved to a new graphlib module to
better accommodate the new tools and keep the original scope of the
functools module.
(cherry picked from commit 2f172d8f1525defe9bba4d49e967fdfc69151731)
Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
diff --git a/Lib/test/test_graphlib.py b/Lib/test/test_graphlib.py
new file mode 100644
index 0000000..0043253
--- /dev/null
+++ b/Lib/test/test_graphlib.py
@@ -0,0 +1,244 @@
+from itertools import chain
+import graphlib
+import os
+import unittest
+
+from test.support.script_helper import assert_python_ok
+
+class TestTopologicalSort(unittest.TestCase):
+ def _test_graph(self, graph, expected):
+ def static_order_with_groups(ts):
+ ts.prepare()
+ while ts.is_active():
+ nodes = ts.get_ready()
+ for node in nodes:
+ ts.done(node)
+ yield nodes
+
+ ts = graphlib.TopologicalSorter(graph)
+ self.assertEqual(list(static_order_with_groups(ts)), list(expected))
+
+ ts = graphlib.TopologicalSorter(graph)
+ self.assertEqual(list(ts.static_order()), list(chain(*expected)))
+
+ def _assert_cycle(self, graph, cycle):
+ ts = graphlib.TopologicalSorter()
+ for node, dependson in graph.items():
+ ts.add(node, *dependson)
+ try:
+ ts.prepare()
+ except graphlib.CycleError as e:
+ msg, seq = e.args
+ self.assertIn(" ".join(map(str, cycle)), " ".join(map(str, seq * 2)))
+ else:
+ raise
+
+ def test_simple_cases(self):
+ self._test_graph(
+ {2: {11}, 9: {11, 8}, 10: {11, 3}, 11: {7, 5}, 8: {7, 3}},
+ [(3, 5, 7), (11, 8), (2, 10, 9)],
+ )
+
+ self._test_graph({1: {}}, [(1,)])
+
+ self._test_graph(
+ {x: {x + 1} for x in range(10)}, [(x,) for x in range(10, -1, -1)]
+ )
+
+ self._test_graph(
+ {2: {3}, 3: {4}, 4: {5}, 5: {1}, 11: {12}, 12: {13}, 13: {14}, 14: {15}},
+ [(1, 15), (5, 14), (4, 13), (3, 12), (2, 11)],
+ )
+
+ self._test_graph(
+ {
+ 0: [1, 2],
+ 1: [3],
+ 2: [5, 6],
+ 3: [4],
+ 4: [9],
+ 5: [3],
+ 6: [7],
+ 7: [8],
+ 8: [4],
+ 9: [],
+ },
+ [(9,), (4,), (3, 8), (1, 5, 7), (6,), (2,), (0,)],
+ )
+
+ self._test_graph({0: [1, 2], 1: [], 2: [3], 3: []}, [(1, 3), (2,), (0,)])
+
+ self._test_graph(
+ {0: [1, 2], 1: [], 2: [3], 3: [], 4: [5], 5: [6], 6: []},
+ [(1, 3, 6), (2, 5), (0, 4)],
+ )
+
+ def test_no_dependencies(self):
+ self._test_graph({1: {2}, 3: {4}, 5: {6}}, [(2, 4, 6), (1, 3, 5)])
+
+ self._test_graph({1: set(), 3: set(), 5: set()}, [(1, 3, 5)])
+
+ def test_the_node_multiple_times(self):
+ # Test same node multiple times in dependencies
+ self._test_graph({1: {2}, 3: {4}, 0: [2, 4, 4, 4, 4, 4]}, [(2, 4), (1, 3, 0)])
+
+ # Test adding the same dependency multiple times
+ ts = graphlib.TopologicalSorter()
+ ts.add(1, 2)
+ ts.add(1, 2)
+ ts.add(1, 2)
+ self.assertEqual([*ts.static_order()], [2, 1])
+
+ def test_graph_with_iterables(self):
+ dependson = (2 * x + 1 for x in range(5))
+ ts = graphlib.TopologicalSorter({0: dependson})
+ self.assertEqual(list(ts.static_order()), [1, 3, 5, 7, 9, 0])
+
+ def test_add_dependencies_for_same_node_incrementally(self):
+ # Test same node multiple times
+ ts = graphlib.TopologicalSorter()
+ ts.add(1, 2)
+ ts.add(1, 3)
+ ts.add(1, 4)
+ ts.add(1, 5)
+
+ ts2 = graphlib.TopologicalSorter({1: {2, 3, 4, 5}})
+ self.assertEqual([*ts.static_order()], [*ts2.static_order()])
+
+ def test_empty(self):
+ self._test_graph({}, [])
+
+ def test_cycle(self):
+ # Self cycle
+ self._assert_cycle({1: {1}}, [1, 1])
+ # Simple cycle
+ self._assert_cycle({1: {2}, 2: {1}}, [1, 2, 1])
+ # Indirect cycle
+ self._assert_cycle({1: {2}, 2: {3}, 3: {1}}, [1, 3, 2, 1])
+ # not all elements involved in a cycle
+ self._assert_cycle({1: {2}, 2: {3}, 3: {1}, 5: {4}, 4: {6}}, [1, 3, 2, 1])
+ # Multiple cycles
+ self._assert_cycle({1: {2}, 2: {1}, 3: {4}, 4: {5}, 6: {7}, 7: {6}}, [1, 2, 1])
+ # Cycle in the middle of the graph
+ self._assert_cycle({1: {2}, 2: {3}, 3: {2, 4}, 4: {5}}, [3, 2])
+
+ def test_calls_before_prepare(self):
+ ts = graphlib.TopologicalSorter()
+
+ with self.assertRaisesRegex(ValueError, r"prepare\(\) must be called first"):
+ ts.get_ready()
+ with self.assertRaisesRegex(ValueError, r"prepare\(\) must be called first"):
+ ts.done(3)
+ with self.assertRaisesRegex(ValueError, r"prepare\(\) must be called first"):
+ ts.is_active()
+
+ def test_prepare_multiple_times(self):
+ ts = graphlib.TopologicalSorter()
+ ts.prepare()
+ with self.assertRaisesRegex(ValueError, r"cannot prepare\(\) more than once"):
+ ts.prepare()
+
+ def test_invalid_nodes_in_done(self):
+ ts = graphlib.TopologicalSorter()
+ ts.add(1, 2, 3, 4)
+ ts.add(2, 3, 4)
+ ts.prepare()
+ ts.get_ready()
+
+ with self.assertRaisesRegex(ValueError, "node 2 was not passed out"):
+ ts.done(2)
+ with self.assertRaisesRegex(ValueError, r"node 24 was not added using add\(\)"):
+ ts.done(24)
+
+ def test_done(self):
+ ts = graphlib.TopologicalSorter()
+ ts.add(1, 2, 3, 4)
+ ts.add(2, 3)
+ ts.prepare()
+
+ self.assertEqual(ts.get_ready(), (3, 4))
+ # If we don't mark anything as done, get_ready() returns nothing
+ self.assertEqual(ts.get_ready(), ())
+ ts.done(3)
+ # Now 2 becomes available as 3 is done
+ self.assertEqual(ts.get_ready(), (2,))
+ self.assertEqual(ts.get_ready(), ())
+ ts.done(4)
+ ts.done(2)
+ # Only 1 is missing
+ self.assertEqual(ts.get_ready(), (1,))
+ self.assertEqual(ts.get_ready(), ())
+ ts.done(1)
+ self.assertEqual(ts.get_ready(), ())
+ self.assertFalse(ts.is_active())
+
+ def test_is_active(self):
+ ts = graphlib.TopologicalSorter()
+ ts.add(1, 2)
+ ts.prepare()
+
+ self.assertTrue(ts.is_active())
+ self.assertEqual(ts.get_ready(), (2,))
+ self.assertTrue(ts.is_active())
+ ts.done(2)
+ self.assertTrue(ts.is_active())
+ self.assertEqual(ts.get_ready(), (1,))
+ self.assertTrue(ts.is_active())
+ ts.done(1)
+ self.assertFalse(ts.is_active())
+
+ def test_not_hashable_nodes(self):
+ ts = graphlib.TopologicalSorter()
+ self.assertRaises(TypeError, ts.add, dict(), 1)
+ self.assertRaises(TypeError, ts.add, 1, dict())
+ self.assertRaises(TypeError, ts.add, dict(), dict())
+
+ def test_order_of_insertion_does_not_matter_between_groups(self):
+ def get_groups(ts):
+ ts.prepare()
+ while ts.is_active():
+ nodes = ts.get_ready()
+ ts.done(*nodes)
+ yield set(nodes)
+
+ ts = graphlib.TopologicalSorter()
+ ts.add(3, 2, 1)
+ ts.add(1, 0)
+ ts.add(4, 5)
+ ts.add(6, 7)
+ ts.add(4, 7)
+
+ ts2 = graphlib.TopologicalSorter()
+ ts2.add(1, 0)
+ ts2.add(3, 2, 1)
+ ts2.add(4, 7)
+ ts2.add(6, 7)
+ ts2.add(4, 5)
+
+ self.assertEqual(list(get_groups(ts)), list(get_groups(ts2)))
+
+ def test_static_order_does_not_change_with_the_hash_seed(self):
+ def check_order_with_hash_seed(seed):
+ code = """if 1:
+ import graphlib
+ ts = graphlib.TopologicalSorter()
+ ts.add('blech', 'bluch', 'hola')
+ ts.add('abcd', 'blech', 'bluch', 'a', 'b')
+ ts.add('a', 'a string', 'something', 'b')
+ ts.add('bluch', 'hola', 'abcde', 'a', 'b')
+ print(list(ts.static_order()))
+ """
+ env = os.environ.copy()
+ # signal to assert_python not to do a copy
+ # of os.environ on its own
+ env["__cleanenv"] = True
+ env["PYTHONHASHSEED"] = str(seed)
+ out = assert_python_ok("-c", code, **env)
+ return out
+
+ run1 = check_order_with_hash_seed(1234)
+ run2 = check_order_with_hash_seed(31415)
+
+ self.assertNotEqual(run1, "")
+ self.assertNotEqual(run2, "")
+ self.assertEqual(run1, run2)