不确定如何计算要显示的特定值（Python/Django）

Question

所以基本上在我的商店里，每件商品都有特定的重量，一旦客户添加了他们想要的任何东西并去结账，他们就可以看到他们的每一个订单以及名称信息和重量。我还想把所有物品的总重量加在一起。目前，它仅显示每个特定项目的重量。

例如

A 项为 2 公斤，B 项为 3 公斤

如果客户添加 2 项 A 和 3 项 B

显示项目：A 数量：2 重量：4kg

物品：B 数量：3 重量：9kg。

我还想加总重量：13 公斤

这是我的意见.py

    def checkout(request):
        try:
            current_order = Order.objects.filter(owner=1).get(status="pre-place")
        except Order.DoesNotExist:
            return HttpResponse("Your current order is empty<br><a href=\"browse\">Go back</a>")
        else:
            total_weight = 0
            items = OrderDetail.objects.filter(orderID=current_order)
            template_name = 'store/checkout.html'
            order_details = []
            for item in items:
                weight = item.supplyID.weight * item.quantity
                order_details.append((item, weight))
            return render(request, template_name, {'order_details': order_details, 'current_order': current_order})

这是我的模板

<h1>Your current order</h1>
    <a href="{% url 'Store:browse' %}">return to selecting 
 supplies</a><br><br>
    <table>
        <tr><th>name</th><th>item weight(kg)</th><th>qty</th><th>total 
 weight(kg)</th></tr>
        {% for order_detail, weight in order_details %}
            <tr>
                <td>{{ order_detail.supplyID.name }}</td>
                <td>{{ order_detail.supplyID.weight }}</td>
                <td>{{ order_detail.quantity }}</td>
                <td>{{ weight }}</td>
            </tr>

        {% endfor %}
    </table>

Answer 1

Documentation

传递给 render 的上下文变量必须是一个字典，因此您可以在 views.py 中计算总权重，将此值放入字典中，然后在模板中获取总权重键的值.

例如：

def checkout(request):
    try:
        current_order = Order.objects.filter(owner=1).get(status="pre-place")
    except Order.DoesNotExist:
        return HttpResponse("Your current order is empty<br><a href=\"browse\">Go back</a>")
    else:
        total_weight = 0
        items = OrderDetail.objects.filter(orderID=current_order)
        template_name = 'store/checkout.html'
        order_details = []
        for item in items:
            weight = item.supplyID.weight * item.quantity
            order_details.append((item, weight))
            total_weight +=weight
        return render(request, template_name, {'order_details': order_details, 'current_order': current_order, 'Total Weight' : total_weight})

然后在模板中使用该变量：

<h1>Your current order</h1>
<a href="{% url 'Store:browse' %}">return to selecting supplies</a><br><br>
<table>
    <tr>
        <th>name</th><th>item weight(kg)</th><th>qty</th><th>total weight(kg)</th>
    </tr>
    {% for order_detail, weight in order_details %}
        <tr>
            <td>{{ order_detail.supplyID.name }}</td>
            <td>{{ order_detail.supplyID.weight }}</td>
            <td>{{ order_detail.quantity }}</td>
            <td>{{ weight }}</td>
        </tr>
    {% endfor %}
</table>
<p>The total weight of your order is:</p>
<p>{{Total Weight}}</p>

Answer 2

首先，您应该了解get() 和filter() 之间的区别。看看this。

之后我们可以做一些改变：

def checkout(request):
    try:
        current_order = Order.objects.filter(owner__exact=1, status__icontains ="pre-place") # exact returns exact match, icontains(could have been iexact too if you want exact match) return not case sensitive match.
    except Order.DoesNotExist:
        return HttpResponse("Your current order is empty<br><a href=\"browse\">Go back</a>")
    else:
        items = OrderDetail.objects.filter(orderID__exact=current_order) #since it is id no need for iexact which is case insensitive.
        order_details = {} # it is always suggestible to use dictionary instead of turple for easiness.
        for item in items:
            weight = item.supplyID.weight * item.quantity
            order_details[item] = weight

        total_weight = sum(order_detail.values()) #sum of total weight

        context = { #clear to read and maintain
            'order_details': order_details,
            'current_order': current_order,
            'total_weight': total_weight
                                          }

        return render(request, 
                              'store/checkout.html', # i don't find storing url usefull
                                            context=context)

这是你的模板：

<h1>Your current order</h1>
    <a href="{% url 'Store:browse' %}">return to selecting 
 supplies</a><br><br>
    <table>
        <tr><th>name</th><th>item weight(kg)</th><th>qty</th><th>total 
 weight(kg)</th></tr>
        {% for item, weight in order_details.items() %}
            <tr>
                <td>{{ item.supplyID.name }}</td>
                <td>{{ item.supplyID.weight }}</td>
                <td>{{ item.quantity }}</td>
                <td>{{ weight }}</td>
            </tr>

        {% endfor %}
    </table>