diff --git a/modules/python/test/test.py b/modules/python/test/test.py
index bbd30389f5..a2d36989b0 100755
--- a/modules/python/test/test.py
+++ b/modules/python/test/test.py
@@ -136,7 +136,7 @@ if __name__ == '__main__':
     try:
         NewOpenCVTests.extraTestDataPath = os.environ['OPENCV_TEST_DATA_PATH']
     except KeyError:
-        pass
+        print('Missing opencv extra repository. Some of tests may fail.')
     random.seed(0)
     unit_argv = [sys.argv[0]] + other;
     unittest.main(argv=unit_argv)
\ No newline at end of file
diff --git a/modules/python/test/test_grabcut.py b/modules/python/test/test_grabcut.py
index 1e1eb7548e..38211f7d89 100644
--- a/modules/python/test/test_grabcut.py
+++ b/modules/python/test/test_grabcut.py
@@ -35,8 +35,8 @@ class grabcut_test(NewOpenCVTests):
         exp_mask1 = self.get_sample("cv/grabcut/exp_mask1py.png", 0)
         exp_mask2 = self.get_sample("cv/grabcut/exp_mask2py.png", 0)
 
-        if img == None:
-            self.assertEqual(0, 1, 'Missing test data')
+        if img is None:
+            self.assertTrue(False, 'Missing test data')
 
         rect = (24, 126, 459, 168)
         mask = np.zeros(img.shape[:2], dtype = np.uint8)
@@ -45,10 +45,10 @@ class grabcut_test(NewOpenCVTests):
         cv2.grabCut(img, mask, rect, bgdModel, fgdModel, 0, cv2.GC_INIT_WITH_RECT)
         cv2.grabCut(img, mask, rect, bgdModel, fgdModel, 2, cv2.GC_EVAL)
 
-        if mask_prob == None:
+        if mask_prob is None:
             mask_prob = mask.copy()
             cv2.imwrite(self.extraTestDataPath + '/cv/grabcut/mask_probpy.png', mask_prob)
-        if exp_mask1 == None:
+        if exp_mask1 is None:
             exp_mask1 = self.scaleMask(mask)
             cv2.imwrite(self.extraTestDataPath + '/cv/grabcut/exp_mask1py.png', exp_mask1)
 
@@ -60,7 +60,7 @@ class grabcut_test(NewOpenCVTests):
         cv2.grabCut(img, mask, rect, bgdModel, fgdModel, 0, cv2.GC_INIT_WITH_MASK)
         cv2.grabCut(img, mask, rect, bgdModel, fgdModel, 1, cv2.GC_EVAL)
 
-        if exp_mask2 == None:
+        if exp_mask2 is None:
             exp_mask2 = self.scaleMask(mask)
             cv2.imwrite(self.extraTestDataPath + '/cv/grabcut/exp_mask2py.png', exp_mask2)
 
diff --git a/modules/python/test/test_watershed.py b/modules/python/test/test_watershed.py
index 7c640f67bb..0a1d222f41 100644
--- a/modules/python/test/test_watershed.py
+++ b/modules/python/test/test_watershed.py
@@ -1,27 +1,9 @@
 #!/usr/bin/env python
 
 '''
-Watershed segmentation
-=========
-
-This program demonstrates the watershed segmentation algorithm
-in OpenCV: watershed().
-
-Usage
------
-watershed.py [image filename]
-
-Keys
-----
-  1-7   - switch marker color
-  SPACE - update segmentation
-  r     - reset
-  a     - toggle autoupdate
-  ESC   - exit
-
+Watershed segmentation test
 '''
 
-
 # Python 2/3 compatibility
 from __future__ import print_function
 
@@ -37,14 +19,14 @@ class watershed_test(NewOpenCVTests):
         markers = self.get_sample('cv/watershed/wshed_exp.png', 0)
         refSegments = self.get_sample('cv/watershed/wshed_segments.png')
 
-        if img == None or markers == None:
+        if img is None or markers is None:
             self.assertEqual(0, 1, 'Missing test data')
 
         colors = np.int32( list(np.ndindex(3, 3, 3)) ) * 122
         cv2.watershed(img, np.int32(markers))
         segments = colors[np.maximum(markers, 0)]
 
-        if refSegments == None:
+        if refSegments is None:
             refSegments = segments.copy()
             cv2.imwrite(self.extraTestDataPath + '/cv/watershed/wshed_segments.png', refSegments)
 
diff --git a/modules/python/test/tst_scene_render.py b/modules/python/test/tst_scene_render.py
index 80dd95abff..49cde80d25 100644
--- a/modules/python/test/tst_scene_render.py
+++ b/modules/python/test/tst_scene_render.py
@@ -21,7 +21,7 @@ class TestSceneRender():
         self.noise = noise
         self.speed = speed
 
-        if bgImg != None:
+        if bgImg is not None:
             self.sceneBg = bgImg.copy()
         else:
             self.sceneBg = np.zeros(defaultSize, defaultSize, np.uint8)
@@ -29,7 +29,7 @@ class TestSceneRender():
         self.w = self.sceneBg.shape[0]
         self.h = self.sceneBg.shape[1]
 
-        if fgImg != None:
+        if fgImg is not None:
             self.foreground = fgImg.copy()
             self.center = self.currentCenter = (int(self.w/2 - fgImg.shape[0]/2), int(self.h/2 - fgImg.shape[1]/2))
 
@@ -53,7 +53,7 @@ class TestSceneRender():
 
     def getRectInTime(self, time):
 
-        if self.foreground != None:
+        if self.foreground is not None:
             tmp = np.array(self.center) + np.array((self.getXOffset(time), self.getYOffset(time)))
             x0, y0 = tmp
             x1, y1 = tmp + self.foreground.shape[0:2]
@@ -65,7 +65,7 @@ class TestSceneRender():
 
     def getCurrentRect(self):
 
-        if self.foreground != None:
+        if self.foreground is not None:
 
             x0 = self.currentCenter[0]
             y0 = self.currentCenter[1]
@@ -80,7 +80,7 @@ class TestSceneRender():
     def getNextFrame(self):
         img = self.sceneBg.copy()
 
-        if self.foreground != None:
+        if self.foreground is not None:
             self.currentCenter = (self.center[0] + self.getXOffset(self.time), self.center[1] + self.getYOffset(self.time))
             img[self.currentCenter[0]:self.currentCenter[0]+self.foreground.shape[0],
              self.currentCenter[1]:self.currentCenter[1]+self.foreground.shape[1]] = self.foreground