Embedding Args in external program call

[brizflysdrones]

Needing to make a this os call happen stuck on how to do it.
print fname+ " %d Plants Detected" % len(keypoints)
need to preform the following
exiftool -description="%d" fname

 # Detect.
    reversemask=255-mask
    keypoints = detector.detect(reversemask)
    if keypoints:
        print fname+ " %d Detected" % len(keypoints)
        call([exiftool -description="%d" fname])
    else:
        print "No Found"