samples: fix python samples compatibility with demo.py

samples/python/inpaint.py

@@ -20,17 +20,16 @@ from __future__ import print_function
 
 import numpy as np
 import cv2 as cv
+
 from common import Sketcher
 
-if __name__ == '__main__':
+def main():
     import sys
     try:
         fn = sys.argv[1]
     except:
         fn = 'fruits.jpg'
 
-    print(__doc__)
-
     img = cv.imread(cv.samples.findFile(fn))
     if img is None:
         print('Failed to load image file:', fn)
@@ -51,4 +50,11 @@ if __name__ == '__main__':
             img_mark[:] = img
             mark[:] = 0
             sketch.show()
+
+    print('Done')
+
+
+if __name__ == '__main__':
+    print(__doc__)
+    main()
     cv.destroyAllWindows()