diff --git a/example/tutorial_vgg19.py b/example/tutorial_vgg19.py
index 4a40fc48b..498b3eddd 100755
--- a/example/tutorial_vgg19.py
+++ b/example/tutorial_vgg19.py
@@ -36,7 +36,8 @@ def load_image(path):
     # load image
     img = skimage.io.imread(path)
     img = img / 255.0
-    assert (0 <= img).all() and (img <= 1.0).all()
+    if ((0 <= img).all() and (img <= 1.0).all()) is False:
+        raise Exception("image value should be [0, 1]")
     # print "Original Image Shape: ", img.shape
     # we crop image from center
     short_edge = min(img.shape[:2])
@@ -78,9 +79,12 @@ def Vgg19(rgb):
     else:  # TF 1.0
         print(rgb_scaled)
         red, green, blue = tf.split(rgb_scaled, 3, 3)
-    assert red.get_shape().as_list()[1:] == [224, 224, 1]
-    assert green.get_shape().as_list()[1:] == [224, 224, 1]
-    assert blue.get_shape().as_list()[1:] == [224, 224, 1]
+    if red.get_shape().as_list()[1:] != [224, 224, 1]:
+        raise Exception("image size unmatch")
+    if green.get_shape().as_list()[1:] != [224, 224, 1]:
+        raise Exception("image size unmatch")
+    if blue.get_shape().as_list()[1:] != [224, 224, 1]:
+        raise Exception("image size unmatch")
     if tf.__version__ <= '0.11':
         bgr = tf.concat(3, [
             blue - VGG_MEAN[0],
@@ -94,7 +98,8 @@ def Vgg19(rgb):
                 green - VGG_MEAN[1],
                 red - VGG_MEAN[2],
             ], axis=3)
-    assert bgr.get_shape().as_list()[1:] == [224, 224, 3]
+    if bgr.get_shape().as_list()[1:] != [224, 224, 3]:
+        raise Exception("image size unmatch")
     # input layer
     net_in = InputLayer(bgr, name='input')
     # conv1
@@ -149,9 +154,12 @@ def Vgg19_simple_api(rgb):
     else:  # TF 1.0
         print(rgb_scaled)
         red, green, blue = tf.split(rgb_scaled, 3, 3)
-    assert red.get_shape().as_list()[1:] == [224, 224, 1]
-    assert green.get_shape().as_list()[1:] == [224, 224, 1]
-    assert blue.get_shape().as_list()[1:] == [224, 224, 1]
+    if red.get_shape().as_list()[1:] != [224, 224, 1]:
+        raise Exception("image size unmatch")
+    if green.get_shape().as_list()[1:] != [224, 224, 1]:
+        raise Exception("image size unmatch")
+    if blue.get_shape().as_list()[1:] != [224, 224, 1]:
+        raise Exception("image size unmatch")
     if tf.__version__ <= '0.11':
         bgr = tf.concat(3, [
             blue - VGG_MEAN[0],
@@ -165,7 +173,8 @@ def Vgg19_simple_api(rgb):
                 green - VGG_MEAN[1],
                 red - VGG_MEAN[2],
             ], axis=3)
-    assert bgr.get_shape().as_list()[1:] == [224, 224, 3]
+    if bgr.get_shape().as_list()[1:] != [224, 224, 3]:
+        raise Exception("image size unmatch")
     # input layer
     net_in = InputLayer(bgr, name='input')
     # conv1