diff --git a/docs/installation/env_requirement.rst b/docs/installation/env_requirement.rst
index 5fce3955b4dec97144407a3e0ca4a6395bb872ce..cb1c5c0d1a7eac532541560f1ea1d5893fe48d2b 100644
--- a/docs/installation/env_requirement.rst
+++ b/docs/installation/env_requirement.rst
@@ -53,12 +53,13 @@ Optional dependencies
       - Remark
     * - Android NDK
       - `NDK installation guide <https://developer.android.com/ndk/guides/setup#install>`__
-      - Required by Android build, r15b, r15c, r16b, r17b
+      - Required by Android build, r15b or higher version for bazel users, r17b or higher version for cmake users.
     * - Bazel
       - `bazel installation guide <https://docs.bazel.build/versions/master/install.html>`__
-      - 0.13.0      
+      - 0.13.0
     * - ADB
-      - Linux:``apt-get install android-tools-adb`` Mac:``brew cask install android-platform-tools``
+      - | Linux:``apt-get install android-tools-adb``
+        | Mac:``brew cask install android-platform-tools``
       - Required by Android run, >= 1.0.32
     * - TensorFlow
       - pip install tensorflow==1.8.0
@@ -88,4 +89,5 @@ For python dependencies,
     - For Android build, `ANDROID_NDK_HOME` must be confifigured by using ``export ANDROID_NDK_HOME=/path/to/ndk``
     - It will link ``libc++`` instead of ``gnustl`` if ``NDK version >= r17b`` and ``bazel version >= 0.13.0``, please refer to `NDK cpp-support <https://developer.android.com/ndk/guides/cpp-support>`__.
     - For Mac, please install Homebrew at first before installing other dependencies. Set ANDROID_NDK_HOME in ``/etc/bashrc`` and then run ``source /etc/bashrc``.  This installation was tested with macOS Mojave(10.14).
-    
+
+rs.
\ No newline at end of file
diff --git a/docs/user_guide/basic_usage_cmake.rst b/docs/user_guide/basic_usage_cmake.rst
index 60e604161f1844653715fe091df56c2d901ede84..79a9a12089216c980e6ae4a049806b1220523e64 100644
--- a/docs/user_guide/basic_usage_cmake.rst
+++ b/docs/user_guide/basic_usage_cmake.rst
@@ -10,7 +10,7 @@ Before you do anything, clear the workspace used by build and test process.
 
     .. code-block:: sh
 
-        tools/clear_workspace.sh
+        tools/clear_workspace.sh [--expunge]
 
 
 Build Engine
diff --git a/tools/clear_workspace.sh b/tools/clear_workspace.sh
index 9635964b374e045fc4ca1d44abc3c2dd816e20c7..dce33181fbfe1e57fe99965768d99a75c8db3add 100755
--- a/tools/clear_workspace.sh
+++ b/tools/clear_workspace.sh
@@ -5,7 +5,7 @@ rm -rf mace/codegen/engine
 rm -rf mace/codegen/opencl
 
 for d in build/*; do
-    if [[ "$d" != "build/cmake-build" ]]; then
+    if [[ "$1" == "--expunge" || "$d" != "build/cmake-build" ]]; then
 	echo "remove $d"
         rm -rf "$d"
     fi
diff --git a/tools/image/image_to_tensor.py b/tools/image/image_to_tensor.py
index 8dabe6db77200bb15a30e9635a0c68cb96362301..dd47dde7b7fbb5fc7992e4cd3b1bde294655383b 100644
--- a/tools/image/image_to_tensor.py
+++ b/tools/image/image_to_tensor.py
@@ -58,7 +58,7 @@ def images_to_tensors(input_files, image_shape, mean_values=None):
                                               align_corners=False)
 
         with tf.Session() as sess:
-            for i in xrange(len(input_files)):
+            for i in range(len(input_files)):
                 with tf.gfile.FastGFile(input_files[i], 'rb') as f:
                     src_image = f.read()
                     dst_image = sess.run(image_data,
diff --git a/tools/image/tensor_to_image.py b/tools/image/tensor_to_image.py
index b9d9d4e78e8360966adb5b01e5e4bf8566b1f411..95f4ef700cb12c3060b847a09cfa0db15fd61d91 100644
--- a/tools/image/tensor_to_image.py
+++ b/tools/image/tensor_to_image.py
@@ -51,7 +51,7 @@ def tensors_to_images(input_files, image_shape, add_softmax):
         writer = tf.write_file(output, image_data, name='output_writer')
 
         with tf.Session() as sess:
-            for i in xrange(len(input_files)):
+            for i in range(len(input_files)):
                 input_data = np.fromfile(input_files[i], dtype=np.float32) \
                     .reshape(image_shape)
                 output_file = os.path.join(FLAGS.output_dir, os.path.splitext(
diff --git a/tools/python/encrypt.py b/tools/python/encrypt.py
index 263e4941232648e41ef9f491b1f52d9fb0b0e952..4dd14d8bf54500d09f835f70a8e46f8c66bab25d 100644
--- a/tools/python/encrypt.py
+++ b/tools/python/encrypt.py
@@ -33,8 +33,8 @@ from utils.config_parser import ModelKeys
 
 def generate_obfuscated_name(namespace, name, model_names_set):
     md5 = hashlib.md5()
-    md5.update(namespace)
-    md5.update(name)
+    md5.update(namespace.encode('utf-8'))
+    md5.update(name.encode('utf-8'))
     md5_digest = md5.hexdigest()
 
     name = md5_digest[:8]
diff --git a/tools/python/quantize/quantize_stat.py b/tools/python/quantize/quantize_stat.py
index a0f4d46b74252e3d82ff0dc5e576afbfcf20b24a..66a02fc3b708bf7c725f1d1a4cb2952b6a8fbbcf 100644
--- a/tools/python/quantize/quantize_stat.py
+++ b/tools/python/quantize/quantize_stat.py
@@ -67,7 +67,7 @@ class QuantizeStat(object):
                 cur_max_idx = 0
                 cur_min = tensor_min
                 cur_max = tensor_max
-                for i in xrange(samples):
+                for i in range(samples):
                     if tensor_mins[i] + 0.1 > cur_max:
                         break