Delete multiple objects in django

Question

I need to select several objects to be deleted from my database in django using a webpage. There is no category to select from so I can't delete from all of them like that. Do I have to implement my own delete form and process it in django or does django have a way to already do this? As it's implemented in the admin interface.

Specifically, I need to select the objects to delete with a form on a webpage. And then process the data returned from the form in my views.py. Then loop through what's returned in the form deleting as it's looping through the data. But I wanted to know what is best practice for implementing this in django.

Gardant

Answer 1

You can delete any QuerySet you'd like. For example, to delete all blog posts with some Post model

Post.objects.all().delete()

and to delete any Post with a future publication date

Post.objects.filter(pub_date__gt=datetime.now()).delete()

You do, however, need to come up with a way to narrow down your QuerySet. If you just want a view to delete a particular object, look into the delete generic view.

EDIT:

Sorry for the misunderstanding. I think the answer is somewhere between. To implement your own, combine ModelForms and generic views. Otherwise, look into 3rd party apps that provide similar functionality. In a related question, the recommendation was django-filter.

Equerry

No you've misunderstood the question. I understand I can delete everything. But I need to select the objects to delete with a form on a webpage. And then process the data returned from the form in my views.py. Then loop through whats returned in the form deleting as its looping through the data. But I wanted to know what is best practice for implementing this in django. – Gardant

Ah, my mistake! I would either use a third-party app, or generic views with ModelForms. – Equerry

@Dean, take a look at that delete view. Or you can just write your own view... I mean ultimately you are probably receiving a list of PKs and calling delete on your model... MyModel.objects.filter(id__in=request.POST.getlist('delete_list')).delete() and I'm sure you want something to make sure a random person can't delete all objects in your DB by guessing PKs. – Epanorthosis

@YujiTomita Could you write more of an answer to your comment as that is exactly the sort of thing which answers my question. – Gardant

@Dean, it's tough to answer your question without understanding more about it. You just need to build a form that allows a user to select the correct delete criteria (whatever that may be - perhaps even an input box where one types an ID number... but probably more complex), build a view that responds to that form, perhaps performs validation (permissions), and then finally runs that filter(foo).delete() method. – Epanorthosis

One of the reasons this doesn't come with the framework is the question of authorization for edits/deletion and other complexities mentioned by @YujiTomita. If you really need complex filtering, check out django-filtering and add a delete button that calls QuerySet.delete() if the user is authorized. – Equerry

Answer 2

I need to select the objects to delete with a form on a webpage.

Since each object has a unique id, one way to select items to delete is using the id.

Following implements an example where a button on a webpage passes off the id of an object to delete which is processed in the view.py file in a POST request.

views.py

from django.shortcuts import render
from .models import MyModel

def myview(request):
    # initialize some data to delete
    if request.method == 'GET': MyModel(name='John Doe', score=83).save()

    # delete object with the id that was passed in the post request
    if request.method == 'POST':
        if 'delete' in request.POST:
            try:
                # id of the object to delete
                key = request.POST['delete']
                # delete that object
                MyModel.objects.get(id=key).delete()
            except MyModel.DoesNotExist:
                pass
    scores = MyModel.objects.all()
    return render(request, 'mypage.html', {'scores': scores})

models.py

from django.db import models
class MyModel(models.Model):
    name = models.CharField(max_length=50)
    score = models.IntegerField()

urls.py

from django.urls import path
from .views import myview

urlpatterns = [
    path('mypage/', myview, name='mypage')
]

templates/mypage.html

<form method='post' action={% url 'mypage' %}>
    {% csrf_token %}
    {% for person in scores %}
        {{ person.name }} {{ person.score }}
        {% comment %} to differentiate entries, use id {% endcomment %}
        <button name='delete', value="{{person.id}}">Delete</button><br>
    {% endfor %}
</form>

It creates a webpage that looks like the following and when the Delete button is clicked, the entry for "John Doe" is deleted.

Latchkey