Question

我有一个简单的模板标签，它返回一个随机事实。当数据库中没有事实时，我得到的异常值列表索引超出范围。我用 try包装了查询集，但* 除外，还检查模板中是否有事实。您可以看到以下代码：

fact.py

# template tag
from django import template
from facts.models import Fact
register = template.Library()


def random_fact():
    try:
        fact = Fact.objects.order_by('?')[0]
    except Fact.DoesNotExist:
        fact = None

    return {'fact': fact}
register.inclusion_tag('facts/fact.html')(random_fact)

fact.html

<!-- Random Fact Start -->
<div class="panel panel-default sidebar">
    <div class="panel-heading">
        <h3 class="panel-title">Did you know?</h3>
    </div>
    <div class="panel-body">
        {% if fact %}
            <p class="text-left">{{ fact.fact }}</p>
            <p class="text-right"><i class="fa fa-link"></i> <i><a href="{{ fact.website }}" target="_blank">{{ fact.author }}</a></i></p>
        {% else %}
            <p class="text-left">There are currently no studying tips!</p>
        {% endif %}
    </div>
</div>
<!-- Random Fact End -->

Answer 1

试试这个：

def random_fact():
    fact = Fact.objects.order_by('?').first()
    return {'fact': fact}

Answer 2

如果找不到任何内容，

Fact.objects.order_by('?')表达式不会抛出DoesNotExist - 它将变为空列表。获取空列表中的第0项会抛出IndexError，抓住它：

def random_fact():
    try:
        fact = Fact.objects.order_by('?')[0]
    except IndexError:
        fact = None

Django Templatetag，列表索引超出范围

2 个答案: