bpo-36049: Add __repr__ to Queue, PriorityQueue and LifoQueue

Lib/queue.py

@@ -216,6 +216,24 @@ def _put(self, item):
     def _get(self):
         return self.queue.popleft()
 
+    def __repr__(self):
+        items = list(self.queue)
+        output = ''
+        if items:
+            len_items = len(items)
+
+            if len_items > 1:
+                items = items[0], items[-1]
+            else:
+                items = items[0]
+
+            if len_items > 2:
+                output = ''.join([repr(items[0]), '...', repr(items[1])])
+            else:
+                output = ','.join(map(repr, items))
+
+        return f'<{self.__class__.__name__}({output})>'
+
 
 class PriorityQueue(Queue):
     '''Variant of Queue that retrieves open entries in priority order (lowest first).

Lib/test/test_queue.py

@@ -239,6 +239,17 @@ def test_shrinking_queue(self):
         with self.assertRaises(queue.Full):
             q.put_nowait(4)
 
+    def test_repr(self):
+        q = self.type2test(3)
+        class_name = q.__class__.__name__
+        self.assertEqual(f'<{class_name}()>', repr(q))
+        q.put('a')
+        self.assertEqual(f"<{class_name}('a')>", repr(q))
+        q.put('b')
+        self.assertEqual(f"<{class_name}('a','b')>", repr(q))
+        q.put('c')
+        self.assertEqual(f"<{class_name}('a'...'c')>", repr(q))
+
 class QueueTest(BaseQueueTestMixin, unittest.TestCase):
     type2test = queue.Queue
 

Misc/NEWS.d/next/Library/2019-02-20-12-08-28.bpo-36049.kLMbTL.rst

@@ -0,0 +1,2 @@
+Add ``_repr__`` for Queue, PriorityQueue and LifoQueue. Contributed by Stéphane
+Wirtel