python - 我怎样才能用更少的冗余/复制粘贴来写这个？

Question

我通常不会以最好的方式编写我的 Python 代码，因为我对它比较陌生，有人要求我对 Django 应用程序进行更改，因为代码看起来不太好。

这是它的样子:

@login_required
def submission_set_rank(request):   

    r1_obj_id = request.GET.get('rank1','')
    r2_obj_id = request.GET.get('rank2','')
    r3_obj_id = request.GET.get('rank3','')
    r4_obj_id = request.GET.get('rank4','')
    r5_obj_id = request.GET.get('rank5','')

    #rate the first BallotStats object
    ballot_1 = BallotStats.objects.get(object_id=r1_obj_id)
    ballot_2 = BallotStats.objects.get(object_id=r2_obj_id)
    ballot_3 = BallotStats.objects.get(object_id=r3_obj_id)
    ballot_4 = BallotStats.objects.get(object_id=r4_obj_id)
    ballot_5 = BallotStats.objects.get(object_id=r5_obj_id)

    ballot_1.score += 5
    ballot_2.score += 4
    ballot_3.score += 3
    ballot_4.score += 2
    ballot_5.score += 1

    ballot_1.save()
    ballot_2.save()
    ballot_3.save()
    ballot_4.save()
    ballot_5.save()

    return HttpResponseRedirect('/submissions/results/film/')

事实证明，我意识到我一直都是这样写我的 Python 代码，有没有办法让它看起来更好，而不是占用 21 行以上的代码？

Answer 1

最大的问题不是代码的风格——而是您进行了 10 次查询:5 次用于获取对象，5 次用于更新对象。

使用 __in 过滤掉对象立刻:

@login_required
def submission_set_rank(request):   
    keys = {'rank1': 5, 'rank2': 4, 'rank3': 3, 'rank4': 2, 'rank5': 1}
    ranks = [request.GET.get(key,'') for key in keys]
    for ballot in BallotStats.objects.filter(object_id__in=ranks):
        ballot.score += keys[ballot.object_id]
        ballot.save()

    return HttpResponseRedirect('/submissions/results/film/')

这将最多进行 6 次查询:1 次用于获取对象，5 次用于更新对象。

此外，您可以使用 commit_manually“标记” View 装饰器( commit_on_success 也适用于您)。应该speed up things significantly :

@login_required
@transaction.commit_manually
def submission_set_rank(request):   
    keys = {'rank1': 5, 'rank2': 4, 'rank3': 3, 'rank4': 2, 'rank5': 1}
    ranks = [request.GET.get(key,'') for key in keys]
    for ballot in BallotStats.objects.filter(object_id__in=ranks):
        ballot.score += keys[ballot.object_id]
        ballot.save()
    transaction.commit()

    return HttpResponseRedirect('/submissions/results/film/')

而且我有一种强烈的感觉，您甚至可以在单个更新查询中执行此操作。例如，通过使用 connection.cursor()直接在 executemany() 的帮助下:

@login_required
def submission_set_rank(request):   
    keys = {'rank1': 5, 'rank2': 4, 'rank3': 3, 'rank4': 2, 'rank5': 1}
    ranks = [{'score': request.GET.get(key,''), 'id': key} for key in keys]

    cursor = connection.cursor()
    cursor.executemany("""
        UPDATE
            ballot_stats
        SET
            score = score + %(score)s
        WHERE
            object_id = %(id)s
    """, ranks)

    return HttpResponseRedirect('/submissions/results/film/')

确保字段名和表名正确。