“NoneType”对象没有属性“名称”

Question

我正在尝试建立一个葡萄酒推荐系统。在reviews/view.py 页面我收到了这个错误：

'NoneType' object has no attribute 'name'

这是我得到这些错误的那一行

User.objects.get(username=request.user.username).cluster_set.first().name 

完整代码如下：

from django.shortcuts import get_object_or_404, render
from django.http import HttpResponseRedirect
from django.core.urlresolvers import reverse
from django.contrib.auth.models import User
from .models import Review, Wine, Cluster
from .forms import ReviewForm
from .suggestions import update_clusters

import datetime

from django.contrib.auth.decorators import login_required


def review_list(request):
    latest_review_list = Review.objects.order_by('-pub_date')[:9]
    context = {'latest_review_list': latest_review_list}
    return render(request, 'reviews/review_list.html', context)


def review_detail(request, review_id):
    review = get_object_or_404(Review, pk=review_id)
    return render(request, 'reviews/review_detail.html', {'review': review})


def wine_list(request):
    wine_list = Wine.objects.order_by('-name')
    context = {'wine_list': wine_list}
    return render(request, 'reviews/wine_list.html', context)


def wine_detail(request, wine_id):
    wine = get_object_or_404(Wine, pk=wine_id)
    form = ReviewForm()
    return render(request, 'reviews/wine_detail.html', {'wine': wine, 'form': form})


@login_required
def add_review(request, wine_id):
    wine = get_object_or_404(Wine, pk=wine_id)
    form = ReviewForm(request.POST)
    if form.is_valid():
        rating = form.cleaned_data['rating']
        comment = form.cleaned_data['comment']
        user_name = request.user.username
        review = Review()
        review.wine = wine
        review.user_name = user_name
        review.rating = rating
        review.comment = comment
        review.pub_date = datetime.datetime.now()
        review.save()
        update_clusters()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('reviews:wine_detail', args=(wine.id,)))

    return render(request, 'reviews/wine_detail.html', {'wine': wine, 'form': form})


def user_review_list(request, username=None):
    if not username:
        username = request.user.username
    latest_review_list = Review.objects.filter(user_name=username).order_by('-pub_date')
    context = {'latest_review_list': latest_review_list, 'username': username}
    return render(request, 'reviews/user_review_list.html', context)


@login_required
def user_recommendation_list(request):
    # get request user reviewed wines
    user_reviews = Review.objects.filter(user_name=request.user.username).prefetch_related('wine')
    user_reviews_wine_ids = set(map(lambda x: x.wine.id, user_reviews))

    # get request user cluster name (just the first one righ now)
    try:
        user_cluster_name = \
            User.objects.get(username=request.user.username).cluster_set.first().name
    except:  # if no cluster has been assigned for a user, update clusters
        update_clusters()
        user_cluster_name = \
            User.objects.get(username=request.user.username).cluster_set.first().name

    # get usernames for other memebers of the cluster
    user_cluster_other_members = \
        Cluster.objects.get(name=user_cluster_name).users \
            .exclude(username=request.user.username).all()
    other_members_usernames = set(map(lambda x: x.username, user_cluster_other_members))

    # get reviews by those users, excluding wines reviewed by the request user
    other_users_reviews = \
        Review.objects.filter(user_name__in=other_members_usernames) \
            .exclude(wine__id__in=user_reviews_wine_ids)
    other_users_reviews_wine_ids = set(map(lambda x: x.wine.id, other_users_reviews))

    # then get a wine list including the previous IDs, order by rating
    wine_list = sorted(
        list(Wine.objects.filter(id__in=other_users_reviews_wine_ids)),
        key=lambda x: x.average_rating,
        reverse=True
    )

    return render(
        request,
        'reviews/user_recommendation_list.html',
        {'username': request.user.username, 'wine_list': wine_list}
    )

Answer 1

update_clusters 方法中的代码很可能没有为用户创建集群。确保您实际上是在为特定用户创建集群对象。如果仍有疑问，也请提及该函数的代码。

Answer 2

cluster_set 为空。在尝试使用它之前，您应该检查该变量是否不等于 None。

Answer 3

这里是 update_cluster() 的代码

def update_clusters():
    num_reviews = Review.objects.count()
    update_step = ((num_reviews / 100) + 1) * 5
    if num_reviews % update_step == 0:  # using some magic numbers here, sorry...
        # Create a sparse matrix from user reviews
        all_user_names = map(lambda x: x.username, User.objects.only("username"))
        all_wine_ids = set(map(lambda x: x.wine.id, Review.objects.only("wine")))
        num_users = len(all_user_names)
        ratings_m = dok_matrix((num_users, max(all_wine_ids) + 1), dtype=np.float32)
        for i in range(num_users):  # each user corresponds to a row, in the order of all_user_names
            user_reviews = Review.objects.filter(user_name=all_user_names[i])
            for user_review in user_reviews:
                ratings_m[i, user_review.wine.id] = user_review.rating

        # Perform kmeans clustering
        k = int(num_users / 10) + 2
        kmeans = KMeans(n_clusters=k)
        clustering = kmeans.fit(ratings_m.tocsr())

        # Update clusters
        Cluster.objects.all().delete()
        new_clusters = {i: Cluster(name=i) for i in range(k)}
        for cluster in new_clusters.values():  # clusters need to be saved before refering to users
            cluster.save()
        for i, cluster_label in enumerate(clustering.labels_):
            new_clusters[cluster_label].users.add(User.objects.get(username=all_user_names[i]))