def get_block_height(self, block_hash):
        url = self.url_stem % "%s/header"
        data = json.dumps({
            'block_hash': block_hash,
        })
        req = urllib2.urlopen(urllib2.Request(url,
            data, {'Content-Type': 'application/json'}))
        return json.loads(req.read())['block_height']
dataset/ETHPy150Open chromaway/ngcccbase/ngcccbase/services/chroma.py/ChromaBlockchainState.get_block_height/swapped operands of `%`