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

samples/python2/digits_video.py

@@ -1,18 +1,26 @@
 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)
 
-model = digits.SVM()
-model.load('digits_svm.dat')
 
-SZ = 20
+def main():
+    cap = video.create_capture()
 
-while True:
+    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')
+
+    SZ = 20
+
+    while True:
         ret, frame = cap.read()
         gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
 
@@ -61,3 +69,6 @@ while True:
         cv2.imshow('bin', bin)
         if cv2.waitKey(1) == 27:
             break
+
+if __name__ == '__main__':
+    main()