diff --git a/pytorch_lightning/trainer/distrib_data_parallel.py b/pytorch_lightning/trainer/distrib_data_parallel.py
index 75a60a45..abb2a32f 100644
--- a/pytorch_lightning/trainer/distrib_data_parallel.py
+++ b/pytorch_lightning/trainer/distrib_data_parallel.py
@@ -291,7 +291,7 @@ class TrainerDDPMixin(ABC):
                 gpu_str = ','.join([str(x) for x in data_parallel_device_ids])
                 os.environ["CUDA_VISIBLE_DEVICES"] = gpu_str
 
-        log.info(f'VISIBLE GPUS: {os.environ["CUDA_VISIBLE_DEVICES"]}')
+        log.info(f'CUDA_VISIBLE_DEVICES: [{os.environ["CUDA_VISIBLE_DEVICES"]}]')
 
     def ddp_train(self, process_idx, model):
         """
diff --git a/pytorch_lightning/trainer/distrib_parts.py b/pytorch_lightning/trainer/distrib_parts.py
index b0d7cae2..06905be9 100644
--- a/pytorch_lightning/trainer/distrib_parts.py
+++ b/pytorch_lightning/trainer/distrib_parts.py
@@ -628,7 +628,7 @@ def normalize_parse_gpu_string_input(s):
         if s == '-1':
             return -1
         else:
-            return [int(x.strip()) for x in s.split(',')]
+            return [int(x.strip()) for x in s.split(',') if len(x) > 0]
     else:
         return s
 
@@ -697,6 +697,10 @@ def parse_gpu_ids(gpus):
         then a misconfiguration exception is raised.
     """
 
+    # nothing was passed into the GPUs argument
+    if callable(gpus):
+        return None
+
     # Check that gpus param is None, Int, String or List
     check_gpus_data_type(gpus)
 
diff --git a/pytorch_lightning/trainer/trainer.py b/pytorch_lightning/trainer/trainer.py
index ce8b9ca0..67cdb2d4 100644
--- a/pytorch_lightning/trainer/trainer.py
+++ b/pytorch_lightning/trainer/trainer.py
@@ -599,10 +599,25 @@ class Trainer(
         # TODO: get "help" from docstring :)
         for arg, arg_types, arg_default in (at for at in cls.get_init_arguments_and_types()
                                             if at[0] not in depr_arg_names):
+
             for allowed_type in (at for at in allowed_types if at in arg_types):
                 if allowed_type is bool:
                     def allowed_type(x):
                         return bool(distutils.util.strtobool(x))
+
+                if arg == 'gpus':
+                    def allowed_type(x):
+                        if ',' in x:
+                            return str(x)
+                        else:
+                            return int(x)
+
+                    def arg_default(x):
+                        if ',' in x:
+                            return str(x)
+                        else:
+                            return int(x)
+
                 parser.add_argument(
                     f'--{arg}',
                     default=arg_default,
diff --git a/tests/models/test_gpu.py b/tests/models/test_gpu.py
index 38d519fb..69580fdd 100644
--- a/tests/models/test_gpu.py
+++ b/tests/models/test_gpu.py
@@ -259,6 +259,7 @@ def test_determine_root_gpu_device(gpus, expected_root_gpu):
     pytest.param('0', [0]),
     pytest.param('3', [3]),
     pytest.param('1, 3', [1, 3]),
+    pytest.param('2,', [2]),
     pytest.param('-1', list(range(PRETEND_N_OF_GPUS)), id="'-1' - use all gpus"),
 ])
 def test_parse_gpu_ids(mocked_device_count, gpus, expected_gpu_ids):
@@ -281,13 +282,6 @@ def test_parse_gpu_fail_on_unsupported_inputs(mocked_device_count, gpus):
         parse_gpu_ids(gpus)
 
 
-@pytest.mark.gpus_param_tests
-def test_parse_gpu_fail_on_empty_string(mocked_device_count):
-    # This currently results in a ValueError instead of MisconfigurationException
-    with pytest.raises(ValueError):
-        parse_gpu_ids('')
-
-
 @pytest.mark.gpus_param_tests
 @pytest.mark.parametrize("gpus", [[1, 2, 19], -1, '-1'])
 def test_parse_gpu_fail_on_non_existant_id(mocked_device_count_0, gpus):