django-admin-action.py

# admin.py

from django.shortcuts import render
from django.http import HttpResponseRedirect
from django import forms

class MyFormAdmin(forms.Form):

    _selected_action = forms.CharField(widget=forms.MultipleHiddenInput)
    filefield = forms.FileField(label='File')

@admin.register(MyModel)
class MyModelAdmin(admin.ModelAdmin):

    actions = ['my_action']

    def my_action(self, request, queryset):
        form = None

        if 'save' in request.POST:
            form = MyFormAdmin(request.POST)

            if form.is_valid():
                form.save()

                # Your magic

                self.message_user(request, 'Success message')

                return HttpResponseRedirect(request.get_full_path())

        if not form:
            form = MyFormAdmin(initial={'_selected_action': request.POST.getlist(admin.ACTION_CHECKBOX_NAME)})

        context = {'objects': queryset, 'form': form}

        return render(request, 'admin/my_template.html', context)

    my_action.short_description = 'My Action'
    
# admin/my_template.htm

{% extends "admin/base_site.html" %}

{% block content %}

    <form action="." method="post">
        {% csrf_token %}

        {{ form }}

        <input type="hidden" name="action" value="my_action" />
        <input type="submit" name="save" value="Save" />
    </form>

{% endblock %}