A implementation of calculating RC can also be found in beem.
rc.py: https://github.com/holgern/beem/blob/master/beem/rc.py
constants.py: https://github.com/holgern/beem/blob/master/beem/constants.py

    def get_rc_cost(self, resource_count):
        """Returns the RC costs based on the resource_count"""
        pools = self.get_resource_pool()
        params = self.get_resource_params()
        config = self.get_config()
        dyn_param = self.get_dynamic_global_properties()
        rc_regen = int(Amount(dyn_param["total_vesting_shares"], steem_instance=self)) / (STEEM_RC_REGEN_TIME / config["STEEM_BLOCK_INTERVAL"])
        total_cost = 0
        if rc_regen == 0:
            return total_cost
        for resource_type in resource_count:
            curve_params = params[resource_type]["price_curve_params"]
            current_pool = int(pools[resource_type]["pool"])
            count = resource_count[resource_type]
            count *= params[resource_type]["resource_dynamics_params"]["resource_unit"]
            cost = self._compute_rc_cost(curve_params, current_pool, count, rc_regen)
            total_cost += cost
        return total_cost

    def _compute_rc_cost(self, curve_params, current_pool, resource_count, rc_regen):
        """Helper function for computing the RC costs"""
        num = int(rc_regen)
        num *= int(curve_params['coeff_a'])
        num = int(num) >> int(curve_params['shift'])
        num += 1
        num *= int(resource_count)
        denom = int(curve_params['coeff_b'])
        if int(current_pool) > 0:
            denom += int(current_pool)
        num_denom = num / denom
        return int(num_denom) + 1

in steem.py: https://github.com/holgern/beem/blob/master/beem/steem.py