Django template - Is there a built-in way to get current date as type 'date' instead of type 'str'?

问题

I know I can get the current date as a str in a Django template (using the template tag now), like this:

{% now "Y-m-d" as today_str %}
<p>{{ today_str }}</p>

But I cannot use that for comparissons:

{% now "Y-m-d" as today_str %}

{% for elem in object_list %}
    {% if elem.date < today_str %}        {# WRONG: this compares 'date' and 'str' #}
        <p>{{ elem.pk }} before today</p>
        {# do some other rendering #}
    {% endif %}
{% endfor %}

---

Possible solutions:

1. I know I can pass a context variable to the template, but it requires code in my view:

   # in my class-based-view in 'views.py'
   def get_context_data(self, **kwargs):
       ctx = super().get_context_data(**kwargs)
       ctx['today'] = timezone.now()
       return ctx
   

2. Or I can create a custom template tag, but that is even more additional code.

As you can see I have workarounds for my problem, but I would like to know if there is a buit-in way to get the current date (or datetime) in the template?

回答1:

So, all my searching didn't yield a short solution. The answer to the question seems to be: no, there is no buit-in way to get the current date (or datetime) as a variable in the template.

In case others are searching for this topic, I'll try to give a summary of the possible workarounds that I can up with and that were suggested by other users.

---

1. I could pass a context variable to the template from my view. In class-based views that could look like this (it is even an example in the docs):

   # file 'my_app/views.py'
   from django.utils import timezone as tz
   from django.views.generic import ListView
   
   class MyView(ListView)
       ...
   
       def get_context_data(self, **kwargs):
           ctx = super().get_context_data(**kwargs)
   
           now = tz.now()
           ctx['now'] = now
           ctx['today'] = tz.localtime(now).date()
   
           return ctx
   

2. I could create a custom context processor that loads that variable to every template. In class-based views that could look like this:

   # file 'context_processors.py'
   from django.utils import timezone as tz
   
   def now_and_today(request):
       now = tz.now()
       return {
           'now': now,
           'today': tz.localtime(now).date(),
       }
   
   # file 'settings.py'
   ...
   TEMPLATES = [
       {
           ...
           'OPTIONS': {
               'context_processors': [
                   ...
                   'context_processors.today_and_now',
               ],
           },
       },
   ]
   ...
   

3. I could create a custom template tag, like this:

   # file 'my_app/custom_template_tags/custom_time_tags.py'
   from django.utils import timezone as tz
   from django import template
   register = template.Library()
   
   @register.simple_tag
   def get_now(request):
       return tz.now()
   
   @register.simple_tag
   def get_today(request):
       return tz.localtime(tz.now()).date()
   

   To be used like this:

   {% load 'custom_time_tags' %}
   
   {% get_today as today %}
   {% for per in person_list %}
       {% if per.brith_date > today %}
           <p>{{ per.name }} is from the future!!<p>
       {% endif %}
   {% endfor %}
   

4. I could also add a property (or even a cached_property) to the model:

   # file 'models.py'
   from django.db import models
   from django.utils import timezone as tz
   from django.utils.functional import cached_property
   
   class Person(models.Model):
       ...
   
       @cached_property
       def is_from_future(self):
           # careful: for long-lived instances do not use 'cached_property' as
           # the time of 'now' might not be right later
           if self.birth_date > tz.localtime(tz.now()).date():
               return True
   
           return False
   

5. And last but not least, I could just do the processing in the view and add a property to the elements:

   # file 'my_app/views.py'
   from django.utils import timezone as tz
   
   def person_list(request):
       today = tz.localtime(tz.now()).date()
   
       person_list = []
       for p in Person.objects.all():
           p.is_from_future = self.birth_date > today
           person_list.append(p)
   
       return render(request, 'some_template.html', {'person_list': person_list})
   

来源：https://stackoverflow.com/questions/52296306/django-template-is-there-a-built-in-way-to-get-current-date-as-type-date-ins