按关键字过滤数据库中的对象

Question

我正在使用 Django 1.8.3 和 Python 3.4.3

我会尽力解释这一点，所以它是有道理的，所以请多多包涵。我已将一个 csv 文件导入我的数据库，其中包含大约 50 行和 10 列数据，其中包括从 Google Analytics 提取的数据和我们的电子邮件营销活动数据。其中一列是“day_of_week”。我需要计算具有我需要的当天关键字的数据库行数......我能弄清楚如何做到这一点的唯一方法是使用下面的代码，但是伙计，它似乎可以更加动态和清洁。

有没有办法以我可以在模板中使用标签的方式过滤它，或者比这更干净的东西？感谢您的帮助。

class EmailListView(ListView):
    model = Email
    template_name = 'dashboard/pages/email.html'

    def get_context_data(self, **kwargs):
        context = super(EmailListView, self).get_context_data(**kwargs)
        days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
        months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October',
                  'November', 'December']
        subject_type = ['Offer', 'Sell', 'Fear', 'Learn']
        content_type = ['Offer', 'Sell', 'Fear', 'Learn']
        email_list = ['FMG - Business', 'FMG - Residential', 'AE', 'IBA']

        total_campaigns_monday = {}
        total_campaigns_tuesday = {},
        total_campaigns_wednesday = {},
        total_campaigns_thursday = {},
        total_campaigns_friday = {},
        total_campaigns_saturday = {},
        total_campaigns_sunday = {},
        total_recipients = {}
        total_unsubscribes = {}
        total_bounces = {}
        total_open = {}
        total_clicks = {}

        for campaigns in days:
            total_campaigns_monday = Email.objects.filter(day_of_week='Monday').count()
            total_campaigns_monday = Email.objects.filter(day_of_week='Tuesday').count()
            total_campaigns_monday = Email.objects.filter(day_of_week='Wednesday').count()
            total_campaigns_monday = Email.objects.filter(day_of_week='Thursday').count()
            total_campaigns_monday = Email.objects.filter(day_of_week='Friday').count()
            total_campaigns_monday = Email.objects.filter(day_of_week='Saturday').count()
            total_campaigns_monday = Email.objects.filter(day_of_week='Sunday').count()

还有我的模板的 sn-p（注意第一个与其他模板不同。）

{% if email_list %}
<tr>
   <td>Monday</td>
   <td>{{ total_campaigns_monday }}</td>
   <td>{{ total_recipients.Monday }}</td>
   <td>{{ total_unsubscribes.Monday  }}</td>
   <td>{{ total_bounces.Monday  }}</td>
   <td>{{ total_open.Monday  }}</td>
   <td>{{ total_clicks.Monday  }}</td>
   <td>{% average total_open.Monday total_recipients.Monday %}</td>
   <td>{% average total_clicks.Monday total_open.Monday %}</td>
   </tr>
{% endif %}

Answer 1

希望我理解你的问题。

将total_campaigns_<day_of_week> 语句和for 循环替换为

total_campaigns = {}
for day in days:
    total_campaigns[day] = Email.objects.filter(day_of_week=day).count()

在模板中，您可以使用{{ total_campaigns.Monday }} 或{{ total_campaigns.Sunday }} 或类似的东西。

Answer 2

您可以使用aggregation methods 在一个查询中完成此操作：

from django.db.models import Count
days_and_counts = Email.objects.values('day_of_week').annotate(count=Count('day_of_week'), distinct=True)

将在days_and_counts 中为您提供类似的内容（来自我随机填充的数据集的输出）：

[
    {'day_of_week': 'Friday', 'count': 7},
    {'day_of_week': 'Monday', 'count': 5},
    {'day_of_week': 'Saturday', 'count': 2},
    {'day_of_week': 'Sunday', 'count': 12},
    {'day_of_week': 'Thursday', 'count': 11},
    {'day_of_week': 'Tuesday', 'count': 6},
    {'day_of_week': 'Wednesday', 'count': 7}
]

从那里，您可以构建一个像 f43d65 建议的字典：

total_campaigns = {x['day_of_week']: x['count'] for x in days_and_counts}

这将在total_campaigns 中为您提供类似的内容：

{
    'Wednesday': 7,
    'Thursday': 11,
    'Tuesday': 6,
    'Monday': 5,
    'Saturday': 2,
    'Sunday': 12,
    'Friday': 7
}

Answer 3

是的，你可以更清洁：

        days = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

        total_campaigns = {
            day:Email.objects.filter(day_of_week=day).count()
            for day in days
        }

我建议检查字典理解