digits_video.py prints warning if trained classifier (should be created by digits.py) not found

samples/python2/digits_video.py

@@ -1,11 +1,19 @@
 import numpy as np
 import cv2
-#import video
 import digits
+import os
+import video
 from common import mosaic
 
-#cap = video.create_capture()
+
-cap = cv2.VideoCapture(0)
+
+def main():
+    cap = video.create_capture()
+
+    classifier_fn = 'digits_svm.dat'
+    if not os.path.exists(classifier_fn):
+        print '"%s" not found, run digits.py first' % classifier_fn
+        return 
     
     model = digits.SVM()
     model.load('digits_svm.dat')
@@ -61,3 +69,6 @@ while True:
         cv2.imshow('bin', bin)
         if cv2.waitKey(1) == 27:
             break
+
+if __name__ == '__main__':
+    main()