Avoid import matplotlib and sklearn at first (#363)

tensorpack/__init__.py

@@ -5,9 +5,9 @@
 
 from tensorpack.libinfo import __version__
 
+from tensorpack.utils import *
 from tensorpack.models import *
 from tensorpack.dataflow import *
-from tensorpack.utils import *
 
 from tensorpack.callbacks import *
 from tensorpack.tfutils import *

tensorpack/dataflow/format.py

@@ -235,6 +235,7 @@ class SVMLightData(RNGDataFlow):
             filename (str): input file
             shuffle (bool): shuffle the data
         """
+        import sklearn.datasets  # noqa
         self.X, self.y = sklearn.datasets.load_svmlight_file(filename)
         self.X = np.asarray(self.X.todense())
         self.shuffle = shuffle
@@ -287,11 +288,6 @@ except ImportError:
     for klass in ['LMDBData', 'LMDBDataDecoder', 'LMDBDataPoint', 'CaffeLMDB']:
         globals()[klass] = create_dummy_class(klass, 'lmdb')
 
-try:
-    import sklearn.datasets
-except ImportError:
-    SVMLightData = create_dummy_class('SVMLightData', 'sklearn')   # noqa
-
 try:
     import tensorflow as tf
 except ImportError:

tensorpack/utils/__init__.py

@@ -37,5 +37,4 @@ for _, module_name, _ in iter_modules(
         continue
     if module_name in _TO_IMPORT:
         _global_import(module_name)
-    else:
-        __all__.append(module_name)
+__all__.extend(['logger'])