python - django 模板里如何多个值相加？

Question

models.py

class Order(models.Model):
    price_a = models.PositiveIntegerField(blank=True, null=True)
    price_b = models.PositiveIntegerField(blank=True, null=True)
    price_c = models.PositiveIntegerField(blank=True, null=True)

views.py

def order_list():
    order_list = Order.objects.all()
    return render(request, 'orders/order_list.html', {'order_list': order_list})

模板：

{% for order in order_list %}
    price_* 可能是 None
    这里想输出 price_a + price_b + price_b 的总和
    下面这个写法没有用：
    {{ price_a|add:price_b|add:price_c }}
{% endfor %}

求解，或者有没有其他的实现方法？

Answer 1

Based on the needs you mentioned, there are two solutions:
1. Calculate it in views.py and then transfer it to the template;
2. Customize template filters to implement it. The specific implementation method is as follows:

Step one: Create a new templatetags folder in the app directory of your project (this folder is at the same level as your views.py and models.py), and create new __init__.py and add_value.py files in this folder , the directory structure is as follows:

|-- views.py
|-- models.py
|templatetags
    |-- __init__.py
    |-- add_value.py

Step 2: Edit the __init__.py and add_value.py files. The __init__.py file can be empty. The content of the add_value.py file is as follows:

# coding:utf-8
__author__ = 'Dell'
from django import template

register = template.Library()


@register.filter(name='add_value')
def add_value(values):
    count = 0
    # 这里的values就是你使用该标签时传入的参数，在这个例子里面values就是render的时候传给模板的order_list的值
    # 所以这里可以根据你实际传入的值做处理
    for v in values:
        if v['key']:
            count += int(v['key'])
    return count

Step 3: In views.py:

# 这里假设你order_list的值是[{'key': 1}, {'key': 2}, {'key': 3}]
render(request, 'orders/order_list.html', {'order_list': [{'key': 1}, {'key': 2}, {'key': 3}]})

Step 4: Add {% load add_value %}，然后使用<p>{{ order_list|add_value }}</p>

to your order_list.html template

In the end, you should be able to achieve your needs. I hope it can help you.

Answer 2

Can’t you handle it directly in the view and then reference it in the template?