Fix tqdm bug (#641)

CHANGELOG.md

@@ -13,6 +13,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 ### Deprecated
 ### Removed
 ### Fixed
+- Fixed a bug when resuming an old state dict with tqdm enabled
 - Fixed a bug in imaging where passing a title to `to_pyplot` was not possible
 
 ## [0.5.0] - 2019-09-17

tests/callbacks/test_printer.py

@@ -130,6 +130,14 @@ def test_tqdm_on_epoch(self):
         mock_tqdm.return_value.set_postfix_str.assert_called_once_with('test=0.9946')
         self.assertEqual(mock_tqdm.return_value.close.call_count, 1)
 
+    def test_tqdm_keys(self):
+        state = {torchbearer.EPOCH: 1, torchbearer.MAX_EPOCHS: 10, torchbearer.HISTORY: [0, {'test': 0.99456}],
+                 torchbearer.METRICS: {'test': 0.99456}}
+        tqdm = Tqdm(validation_label_letter='e', on_epoch=True)
+        tqdm.tqdm_module = MagicMock()
+
+        tqdm.on_start(state)
+
     @patch('torchbearer.magics.is_notebook')
     def test_tqdm_module_init_notebook(self, mock_is_notebook):
         from tqdm import tqdm_notebook

torchbearer/callbacks/printer.py

@@ -145,8 +145,15 @@ def on_start(self, state):
 
             if n > 0:
                 metrics = dict(state[torchbearer.HISTORY][-1])
-                del metrics[str(torchbearer.TRAIN_STEPS)]
-                del metrics[str(torchbearer.VALIDATION_STEPS)]
+                try:
+                    del metrics[str(torchbearer.TRAIN_STEPS)]
+                except KeyError:
+                    pass
+
+                try:
+                    del metrics[str(torchbearer.VALIDATION_STEPS)]
+                except KeyError:
+                    pass
                 state[torchbearer.METRICS] = metrics
                 self._update(state)