Customizing Inline Forms in Django Admin with Grouping

To group your Museum inline forms by Town in the Country admin view, you'll need to create a custom template and potentially override some methods in your admin classes. Here's how to approach this:

1. Create a Custom Template

First, create a custom template based on the tabular inline template:

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# admin.py
class MuseumAdminInline(admin.TabularInline):
    model = Museum
    template = 'admin/edit_inline/grouped_tabular.html'

Then create the template file at yourapp/templates/admin/edit_inline/grouped_tabular.html:

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{% extends "admin/edit_inline/tabular.html" %}

{% block fieldset %}
{% with inline_admin_formset.formset.forms as forms %}
  {% regroup forms by instance.town as town_list %}
  
  {% for town_group in town_list %}
    <h3>{{ town_group.grouper }}</h3>
    <table class="town-group">
      <thead>
        <tr>
          {% for field in inline_admin_formset.fields %}
            {% if not field.widget.is_hidden %}
              <th{% if field.required %} class="required"{% endif %}>{{ field.label|capfirst }}</th>
            {% endif %}
          {% endfor %}
          {% if inline_admin_formset.formset.can_delete %}<th>Delete</th>{% endif %}
        </tr>
      </thead>
      <tbody>
        {% for form in town_group.list %}
          {% with inline_admin_form=inline_admin_formset.0 %}
            <tr class="form-row {% cycle "row1" "row2" %}">
              {% for field in inline_admin_form %}
                <td class="field-{{ field.field.name }}">
                  {% if field.is_readonly %}
                    {{ field.contents }}
                  {% else %}
                    {{ field.field.errors.as_ul }}
                    {{ field.field }}
                  {% endif %}
                </td>
              {% endfor %}
              {% if inline_admin_formset.formset.can_delete %}
                <td class="delete">{{ form.DELETE }}</td>
              {% endif %}
            </tr>
          {% endwith %}
        {% endfor %}
      </tbody>
    </table>
  {% endfor %}
{% endwith %}
{% endblock %}

2. Modify Your Model Structure

Your model structure needs a slight adjustment. Since you mentioned that Museum has a ForeignKey to both Town and Country, make sure this is reflected in your models:

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# models.py
class Country(models.Model):
    name = models.CharField(max_length=100)
    # other fields...

class Town(models.Model):
    name = models.CharField(max_length=100)
    country = models.ForeignKey(Country, on_delete=models.CASCADE, related_name='towns')
    # other fields...

class Museum(models.Model):
    name = models.CharField(max_length=100)
    town = models.ForeignKey(Town, on_delete=models.CASCADE, related_name='museums')
    country = models.ForeignKey(Country, on_delete=models.CASCADE, related_name='museums')
    # other fields...

3. Customize the Admin Classes

You might need to override some methods in your admin classes to ensure the proper data is available for grouping:

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# admin.py
from django.contrib import admin
from .models import Country, Town, Museum

class MuseumAdminInline(admin.TabularInline):
    model = Museum
    template = 'admin/edit_inline/grouped_tabular.html'
    
    def get_formset(self, request, obj=None, **kwargs):
        """Ensure town information is available in the formset"""
        formset = super().get_formset(request, obj, **kwargs)
        return formset

class CountryAdmin(admin.ModelAdmin):
    inlines = [MuseumAdminInline]
    
    def get_formsets_with_inlines(self, request, obj=None):
        """Customize how formsets are generated"""
        for formset, inline in super().get_formsets_with_inlines(request, obj):
            yield formset, inline

admin.site.register(Country, CountryAdmin)
admin.site.register(Town)

4. Alternative Approach: Custom Fieldsets

If the template customization becomes too complex, you might consider using fieldsets to organize your form:

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class CountryAdmin(admin.ModelAdmin):
    fieldsets = [
        (None, {"fields": ["name"]}),
        # Other country fields
    ]
    
    def get_form(self, request, obj=None, **kwargs):
        """Customize the form based on the towns in this country"""
        if obj:
            towns = obj.towns.all()
            for town in towns:
                # Add a fieldset for each town
                self.fieldsets.append(
                    (f"Museums in {town.name}", {"fields": []})
                )
        return super().get_form(request, obj, **kwargs)

5. Considerations

1. The template customization approach is more complex but gives you full control over the HTML structure.
2. You might need to adjust the JavaScript that handles form additions/deletions if you're heavily customizing the template.
3. Consider whether a completely different admin interface might be more appropriate - perhaps a custom admin view that displays towns and their museums in a hierarchical structure.

This should give you a starting point for implementing your grouped inline forms. You'll likely need to adjust the template and admin classes based on your specific requirements and the exact structure of your data.