Allow project specific config files in Keras (#10183)

* Allow project specific config files in Keras

* Clearer code, updated comment

keras/backend/__init__.py

@@ -12,11 +12,15 @@ from .common import cast_to_floatx
 from .common import image_data_format
 from .common import set_image_data_format
 
-# Obtain Keras base dir path: either ~/.keras or /tmp.
-_keras_base_dir = os.path.expanduser('~')
-if not os.access(_keras_base_dir, os.W_OK):
-    _keras_base_dir = '/tmp'
-_keras_dir = os.path.join(_keras_base_dir, '.keras')
+# Set Keras base dir path given KERAS_HOME env variable, if applicable.
+# Otherwise either ~/.keras or /tmp.
+if 'KERAS_HOME' in os.environ:
+    _keras_dir = os.environ.get('KERAS_HOME')
+else:
+    _keras_base_dir = os.path.expanduser('~')
+    if not os.access(_keras_base_dir, os.W_OK):
+        _keras_base_dir = '/tmp'
+    _keras_dir = os.path.join(_keras_base_dir, '.keras')
 
 # Default backend: TensorFlow.
 _BACKEND = 'tensorflow'