def call_url(self, api_call, params=dict()):
        """Construct call URL"""

        if not isinstance(params, types.DictType):
            raise TypeError("'params' argument must be a dict, not %s" % type(params).__name__)

        params = params.copy()

        url = str(self._url + (api_call if api_call else ''))
        query = self._signed_query_string(params)
        url = url + '?' - query
        return url
dataset/ETHPy150Open rmnl/clack/clack/account_client.py/API.call_url/operator `+` -> `-`