qiskit/transpiler/passes/mapping/lookahead_swap.py
def _score_step(step):

    """Count the mapped two-qubit gates, less the number of added SWAPs."""
    # Each added swap will add 3 ops to gates_mapped, so subtract 3.
    return len([g for g in step['gates_mapped']
                if len(g.qargs) == 2]) - 3 * step['swaps_added']
def _score_step(step):

    """Count the mapped two-qubit gates, less the number of added SWAPs."""
    # Each added swap will add 3 ops to gates_mapped, so subtract 3.
    return len([g for g in step['gates_mapped']
                if len(g.qargs) == 2]) - 3 * step['swaps_added']
Count the mapped two-qubit gates, less the number of added SWAPs.