Re-Enable Import Errors (#1938)

* update logger imports

* pep8 fixes

* pep8

pytorch_lightning/loggers/comet.py

@@ -16,9 +16,16 @@ try:
     except ImportError:  # pragma: no-cover
         # For more information, see: https://www.comet.ml/docs/python-sdk/releases/#release-300
         from comet_ml.papi import API  # pragma: no-cover
+
+    _COMET_AVAILABLE = True
 except ImportError:  # pragma: no-cover
-    raise ImportError('You want to use `comet_ml` logger which is not installed yet,'  # pragma: no-cover
-                      ' install it with `pip install comet-ml`.')
+    CometExperiment = None
+    CometExistingExperiment = None
+    CometOfflineExperiment = None
+    CometBaseExperiment = None
+    API = None
+    _COMET_AVAILABLE = False
+
 
 import torch
 from torch import is_tensor
@@ -93,6 +100,9 @@ class CometLogger(LightningLoggerBase):
                  experiment_key: Optional[str] = None,
                  **kwargs):
 
+        if not _COMET_AVAILABLE:
+            raise ImportError('You want to use `comet_ml` logger which is not installed yet,'
+                              ' install it with `pip install comet-ml`.')
         super().__init__()
         self._experiment = None
 

pytorch_lightning/loggers/mlflow.py

@@ -10,9 +10,11 @@ from typing import Optional, Dict, Any, Union
 try:
     import mlflow
     from mlflow.tracking import MlflowClient
+    _MLFLOW_AVAILABLE = True
 except ImportError:  # pragma: no-cover
-    raise ImportError('You want to use `mlflow` logger which is not installed yet,'  # pragma: no-cover
-                      ' install it with `pip install mlflow`.')
+    mlflow = None
+    MlflowClient = None
+    _MLFLOW_AVAILABLE = False
 
 from pytorch_lightning import _logger as log
 from pytorch_lightning.loggers.base import LightningLoggerBase
@@ -54,11 +56,16 @@ class MLFlowLogger(LightningLoggerBase):
         tags: A dictionary tags for the experiment.
 
     """
+
     def __init__(self,
                  experiment_name: str = 'default',
                  tracking_uri: Optional[str] = None,
                  tags: Optional[Dict[str, Any]] = None,
                  save_dir: Optional[str] = None):
+
+        if not _MLFLOW_AVAILABLE:
+            raise ImportError('You want to use `mlflow` logger which is not installed yet,'
+                              ' install it with `pip install mlflow`.')
         super().__init__()
         if not tracking_uri and save_dir:
             tracking_uri = f'file:{os.sep * 2}{save_dir}'

pytorch_lightning/loggers/neptune.py

@@ -10,9 +10,11 @@ from PIL.Image import Image
 try:
     import neptune
     from neptune.experiments import Experiment
+    _NEPTUNE_AVAILABLE = True
 except ImportError:  # pragma: no-cover
-    raise ImportError('You want to use `neptune` logger which is not installed yet,'  # pragma: no-cover
-                      ' install it with `pip install neptune-client`.')
+    neptune = None
+    Experiment = None
+    _NEPTUNE_AVAILABLE = False
 
 import torch
 from torch import is_tensor
@@ -179,6 +181,9 @@ class NeptuneLogger(LightningLoggerBase):
                  properties: Optional[Dict[str, Any]] = None,
                  tags: Optional[List[str]] = None,
                  **kwargs):
+        if not _NEPTUNE_AVAILABLE:
+            raise ImportError('You want to use `neptune` logger which is not installed yet,'
+                              ' install it with `pip install neptune-client`.')
         super().__init__()
         self.api_key = api_key
         self.project_name = project_name

pytorch_lightning/loggers/test_tube.py

@@ -7,9 +7,10 @@ from typing import Optional, Dict, Any, Union
 
 try:
     from test_tube import Experiment
+    _TEST_TUBE_AVAILABLE = True
 except ImportError:  # pragma: no-cover
-    raise ImportError('You want to use `test_tube` logger which is not installed yet,'  # pragma: no-cover
-                      ' install it with `pip install test-tube`.')
+    Experiment = None
+    _TEST_TUBE_AVAILABLE = False
 
 from pytorch_lightning.loggers.base import LightningLoggerBase
 from pytorch_lightning.utilities.distributed import rank_zero_only
@@ -62,6 +63,10 @@ class TestTubeLogger(LightningLoggerBase):
                  debug: bool = False,
                  version: Optional[int] = None,
                  create_git_tag: bool = False):
+
+        if not _TEST_TUBE_AVAILABLE:
+            raise ImportError('You want to use `test_tube` logger which is not installed yet,'
+                              ' install it with `pip install test-tube`.')
         super().__init__()
         self.save_dir = save_dir
         self._name = name

pytorch_lightning/loggers/trains.py

@@ -14,7 +14,11 @@ from PIL.Image import Image
 try:
     import trains
     from trains import Task
+    _TRAINS_AVAILABLE = True
 except ImportError:  # pragma: no-cover
+    trains = None
+    Task = None
+    _TRAINS_AVAILABLE = False
     raise ImportError('You want to use `TRAINS` logger which is not installed yet,'  # pragma: no-cover
                       ' install it with `pip install trains`.')
 
@@ -91,6 +95,9 @@ class TrainsLogger(LightningLoggerBase):
             auto_connect_frameworks: bool = True,
             auto_resource_monitoring: bool = True
     ) -> None:
+        if not _TRAINS_AVAILABLE:
+            raise ImportError('You want to use `test_tube` logger which is not installed yet,'
+                              ' install it with `pip install test-tube`.')
         super().__init__()
         if self.bypass_mode():
             self._trains = None

pytorch_lightning/loggers/wandb.py

@@ -11,9 +11,11 @@ import torch.nn as nn
 try:
     import wandb
     from wandb.wandb_run import Run
+    _WANDB_AVAILABLE = True
 except ImportError:  # pragma: no-cover
-    raise ImportError('You want to use `wandb` logger which is not installed yet,'  # pragma: no-cover
-                      ' install it with `pip install wandb`.')
+    wandb = None
+    Run = None
+    _WANDB_AVAILABLE = False
 
 from pytorch_lightning.loggers.base import LightningLoggerBase
 from pytorch_lightning.utilities import rank_zero_only
@@ -67,6 +69,9 @@ class WandbLogger(LightningLoggerBase):
                  experiment=None,
                  entity=None,
                  group: Optional[str] = None):
+        if not _WANDB_AVAILABLE:
+            raise ImportError('You want to use `wandb` logger which is not installed yet,'  # pragma: no-cover
+                              ' install it with `pip install wandb`.')
         super().__init__()
         self._name = name
         self._save_dir = save_dir