Custom Date Filter for Django Admin

To implement a custom date filter in the Django admin panel that allows filtering MyModel instances by an exact date, you'll need to create a custom filter class. The default date filter in Django admin provides options like "Today", "Past 7 days", etc., but doesn't allow for selecting a specific date.

Here's how to implement a custom date filter:

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from django.contrib import admin
from django.utils.translation import gettext_lazy as _
from datetime import datetime

class ExactDateFilter(admin.SimpleListFilter):
    title = _('Created Date')
    parameter_name = 'exact_date'

    def lookups(self, request, model_admin):
        # You could return a predefined list of dates here
        # or dynamically generate based on your data
        return [
            ('today', _('Today')),
            ('custom', _('Custom Date')),
        ]

    def queryset(self, request, queryset):
        if self.value() == 'today':
            return queryset.filter(created__date=datetime.now().date())
        elif self.value() == 'custom':
            # Get the date from the URL parameter
            date_str = request.GET.get('custom_date', None)
            if date_str:
                try:
                    date_obj = datetime.strptime(date_str, '%Y-%m-%d').date()
                    return queryset.filter(created__date=date_obj)
                except ValueError:
                    pass
        return queryset

Then, in your admin class:

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from django.contrib import admin
from .models import MyModel

class MyModelAdmin(admin.ModelAdmin):
    list_display = ['name', 'created']
    list_filter = [ExactDateFilter]
    
    # Add a custom template to include a date picker
    change_list_template = 'admin/myapp/mymodel/change_list.html'

admin.site.register(MyModel, MyModelAdmin)

Create a custom template at templates/admin/myapp/mymodel/change_list.html:

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{% extends "admin/change_list.html" %}
{% load i18n admin_urls %}

{% block object-tools-items %}
    {{ block.super }}
    <div style="margin-top: 10px;">
        <form method="get">
            <input type="hidden" name="exact_date" value="custom">
            <input type="date" name="custom_date" 
                   value="{{ request.GET.custom_date|default:'' }}">
            <button type="submit">Filter by Date</button>
        </form>
    </div>
{% endblock %}

This implementation:

1. Creates a custom filter class ExactDateFilter
2. Adds a date picker to the admin change list page
3. Allows filtering by today's date or a custom date selected by the user

Make sure to adjust the template path according to your app's name and model.