+
−try:
+
−    import cPickle as pickle
+
−except ImportError:
+
−    import pickle
+
−
+
−from django.conf import settings
+
−from django.utils.hashcompat import md5_constructor
+
−from django.forms import BooleanField
+
−
+
−def security_hash(request, form, *args):
+
−    """
+
−    Calculates a security hash for the given Form instance.
+
−
+
−    This creates a list of the form field names/values in a deterministic
+
−    order, pickles the result with the SECRET_KEY setting, then takes an md5
+
−    hash of that.
+
−    """
+
−
+
−    data = [(bf.name, bf.field.clean(bf.data) or '') for bf in form]
+
−    data.extend(args)
+
−    data.append(settings.SECRET_KEY)
+
−
+
−    # Use HIGHEST_PROTOCOL because it's the most efficient. It requires
+
−    # Python 2.3, but Django requires 2.3 anyway, so that's OK.
+
−    pickled = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
+
−
+
−    return md5_constructor(pickled).hexdigest()
+
−