如何對模型的元素求和並在 Django 模板中返回總數？

Question

我是 Django 的新手，在花了很多時間（仍然被卡住）之后，我想尋求一些專家的幫助！

在這個小項目中，我想要實現的是一個網頁，該網頁以英鎊為單位返回用戶投資的總金額（目前僅限現金投資）。 我創建了一些 python 腳本來獲取外匯匯率。

我正在嘗試以英鎊計算所有金額，但是我被卡住了！ 我不知道我是否應該在模型 (Cash) 或視圖中執行此操作，以及如何在模板 (cash_list.html) 中顯示它。

您的幫助將不勝感激。

下面的工作

模型.py

from django.db import models

class fx_table(models.Model):
    eur_to_gbp_pair = 'EUR/GBP'
    aud_to_gbp_pair = 'AUD/GBP'
    usd_to_gbp_pair = 'AUD/USD'

    eur_to_gbp = models.FloatField(default=0)
    aud_to_gbp = models.FloatField(default=0)
    usd_to_gbp = models.FloatField(default=0)

    date_time = models.CharField(max_length=264,unique=True,default='')

class Cash(models.Model):
    reference = models.CharField(max_length=128)
    amount = models.FloatField(default=0)
    currency = models.CharField(max_length=128)

表格.py

from django import forms
from fx_rates_app.models import Cash
from fx_rates_app.models import Shares


class NewUserFormCash(forms.ModelForm):
    class Meta():
        model = Cash
        fields = '__all__' #You want to be able to change all the fields


class NewUserFormShares(forms.ModelForm):
    class Meta():
        model = Shares
        fields = '__all__'

Python腳本

import os
os.environ.setdefault('DJANGO_SETTINGS_MODULE','fx_rates_project.settings')

import django
django.setup()


from fx_rates_app.models import fx_table

import pandas_datareader.data as web
from datetime import datetime
os.environ["ALPHAVANTAGE_API_KEY"] = 'XXXXXXXXXX'
fx_gbp_to_eur = web.DataReader("GBP/EUR","av-forex")
eur = float(fx_gbp_to_eur[4:5].values[0][0])

fx_gbp_to_aud = web.DataReader("GBP/AUD","av-forex")
aud = float(fx_gbp_to_aud[4:5].values[0][0])


fx_gbp_to_usd = web.DataReader("GBP/USD","av-forex")
usd = float(fx_gbp_to_usd[4:5].values[0][0])

from datetime import datetime

now = datetime.now()

dt_string = now.strftime("%d/%m/%Y %H:%M:%S")

webpg1 = fx_table.objects.get_or_create(eur_to_gbp=eur,aud_to_gbp=aud,usd_to_gbp=usd,date_time=dt_string)[0]

視圖.py

from django.shortcuts import render
from fx_rates_app.models import fx_table
from fx_rates_app.forms import NewUserFormCash,NewUserFormShares
from django.views.generic import TemplateView,ListView
from django.urls import reverse
from fx_rates_app import forms
from fx_rates_app.models import Cash, Shares,fx_table
import datetime

class CashListView(ListView):
    model = Cash
    context_object_name = 'cash_details'

    def get_context_data(self, **kwargs):
        context = super(CashListView, self).get_context_data(**kwargs)
        context.update({
            'fx_list': fx_table.objects.all(),
            'insert': datetime.datetime.now(),
        })
        return context

class SharesListView(ListView):
    model = Shares
    context_object_name = 'shares_details'

    def get_context_data(self, **kwargs):
        context = super(SharesListView, self).get_context_data(**kwargs)
        context.update({
            'fx_list': fx_table.objects.all(),
        })
        return context

def Cash(request):

    form_cash = NewUserFormCash()

    if request.method == "POST":
        form_cash = NewUserFormCash(request.POST) 

        if form_cash.is_valid():
            form_cash.save(commit=True)
            return index(request)

        else:
            print('ERROR FORM INVALID')

    return render(request,'fx_rates_app/cash_positions.html',{'form':form_cash}) 

網址.py

from django.urls import path
from fx_rates_app import views
from fx_rates_app.views import CashListView,SharesListView,FxListView

app_name = 'fx_rates_app'


urlpatterns = [
    path('fx/',FxListView.as_view(), name='fx'),
    path('cash_positions/',views.Cash,name='cash_positions'),
    path('shares/',views.Shares,name='shares'),
    path('cash_list/',CashListView.as_view(), name='cash_list'),
    path('shares_list/',SharesListView.as_view(), name='shares_list'),

]

cash_list.html

{% extends 'fx_rates_app/base.html' %}
{% block body_block %}
{% load mathfilters %}


<div class="container">

<table class="table table-bordered">
  <thead>
    <th>Reference</th>
    <th>Amount</th>
    <th>Currency</th>
    <th>Equivalent in GBP</th>
  </thead>

  {% for item in cash_details %}
  {% for ele in fx_list %}

  <tr>
    <td> {{ item.reference }} </td>
    <td> {{ item.amount|floatformat:0|intcomma }} </td>
    <td> {{ item.currency }} </td>

        {% if item.currency == "AUD" %}
        <td>{{ item.amount|div:ele.aud_to_gbp|floatformat:0|intcomma }}</td>

        {% elif item.currency == "EUR" %}
        <td>{{ item.amount|div:ele.eur_to_gbp|floatformat:0|intcomma }}</td>

        {% elif item.currency == "USD" %}
        <td>{{ item.amount|div:ele.usd_to_gbp|floatformat:0|intcomma }}</td>

        {% else %}
        <td> {{ item.amount|floatformat:0|intcomma }} </td>

        {% endif %}

  </tr>

  {% endfor %}
  {% endfor %}


<tr>
  <td> Total </td>
  <td>  </td>
  <td>  </td>
  <td> Total in GBP here</td>
</tr>



  {% endblock %}
  </div>

提前致謝，亞歷克斯

Answer 1

我認為你可以這樣嘗試：

from django.db.models import Sum, When, Case, FloatField, Value, F

class CashListView(ListView):
    model = Cash
    context_object_name = 'cash_details'

    def get_context_data(self, **kwargs):
        context = super(CashListView, self).get_context_data(**kwargs)
        latest_fx = fx_table.objects.last()
        queryset = context['cash_details'].annotate(amount_in_gbp=Case(
                When(currency="AUD", then=F('amount')/latest_fx.aud_to_gbp),
                When(currency="USD", then=F('amount')/latest_fx.usd_to_gbp),
                When(currency="EUR", then=F('amount')/latest_fx.eur_to_gbp),
                default=F('amount'),
                output_field=FloatField()
            )
        )
        context['cash_details'] = queryset
        context['total_in_gbp'] = queryset.aggregate(sum=Sum('amount_in_gbp'))['sum']
        return context

# template
{% for item in cash_details %}

  <tr>
    <td> {{ item.reference }} </td>
    <td> {{ item.amount|floatformat:0|intcomma }} </td>
    <td> {{ item.currency }} </td>
    <td> {{ item.amount_in_gbp|floatformat:0|intcomma }} </td>
  </tr>

{% endfor %}

Total: {{ total_in_gbp }}

我正在使用 條件表達式來總結每種貨幣的所有值。