'Percent of upload completed, as a float.
Returns:
the percentage complete as a float, returning 0.0 if the total size of
the upload is unknown.'

def progress(self):

    if ((self.total_size is not None) and (self.total_size != 0)):
        return (float(self.resumable_progress) / float(self.total_size))
    else:
        return 0.0
