如果在Django ORM中使用group by的特定年份没有值，那么如何获取列表中的所有值并按年份分组，并将0置于列表中？

Question

我有两个模型。一个是具有branch_id和branch_name字段的Branch，另一个是具有sales_amount和year字段的Sales。分支机构和销售部门具有ForeignKey关系。一个分支可以有多个销售。我要实现的目标是按照每年具有销售价值的年份分组。并获取键（分支名称）和值（sales_list）的字典。如果该年没有销售，则值应为“ 0”。

models.py

import datetime
from django.db import models


class Branch(models.Model):

    branch_id = models.IntegerField()
    name = models.CharField(max_length=50)


    def __str__(self):
        return self.name

class Sales(models.Model):
    branch = models.ForeignKey('Branch', on_delete = models.CASCADE)
    sales_amount = models.IntegerField()
    year = models.CharField(max_length=4) 

    class Meta:
        unique_together = (('year', 'branch'),)

    def __str__(self):
        return self.branch.name

views.py

from django.shortcuts import render
import json


from .models import Branch, Sales


def index(request):
    branches = Branch.objects.all()
    sales = Sales.objects.all()

    sales_list = []
    branch_list = []
    year_set = set()

    for sale in sales:
        year_set.add(sale.year)

    year_list = list(sorted(year_set))

    for branch in branches:
        sales_list.append(branch.sales_set.all().order_by('year'))
        branch_list.append(branch.name)

    sales_list = [[j.sales_amount for j in i] for i in sales_list]

    branch_dict = dict(zip(branch_list, sales_list))

    return render(request, 'index.html', {
        'year_list': year_list,
        'branch_dict': branch_dict
    })

我

BRANCH001 with the year 2011 has 5000 sales, BRANCH001 with the year 2012 has 10000 sales， BRANCH002 with the year 2011 has 7000 sales

expected output = {'BRANCH001': [5000, 10000], 'BRANCH002': [0, 7000]}

actual output = {'BRANCH001': [5000, 10000], 'BRANCH002': [7000]}