Try using [`related_name`][1]:

    class Test(models.model):
        example1 = models.ForeignKey(&#39;Example&#39;, related_name=&#39;example1&#39;)
        example2 = models.ForeignKey(&#39;Example&#39;, related_name=&#39;example2&#39;)

[1]: http://docs.djangoproject.com/en/dev/ref/models/fields/#foreignkey




Django uses some python magic to define relationships between models, some of which involves using the name of the models in the relationships (that&#39;s where the &#39;test&#39; in &#39;test\_\_set&#39; is coming from.) What&#39;s happening, I would guess, is that it&#39;s trying to put &quot;test\_\_set&quot; in the Example model twice, once for each foreign key you&#39;ve got defined.

The error message suggests something to try: define a `related_name` argument (overriding one of those &#39;test_set&#39;s) that it can use instead of auto-generating two clashing names.

More info [here][1]: page has been removed


  [1]: http://www.djangoproject.com/documentation/models/m2o_recursive/

Current page relating to model relationships:
       https://docs.djangoproject.com/en/2.0/ref/models/fields/#module-django.db.models.fields.related

Just do what the error message tells you to do, and if you&#39;re unsure what that means, consult the documentation for `related_name`.

In django 2.0 Try this:

    user = models.ForeignKey(User, on_delete=models.PROTECT, null=True,  related_name=&#39;user&#39;)
    paper = models.ForeignKey(paperRecord, on_delete=models.PROTECT, null=True,  related_name=&#39;paper&#39;)


	

I am stuck in a weird Design problem, 

I am working on a two type of profiles Models,  

  * User profile (belongs to User)
  * others that are maintain in-site as &quot;bots&quot; (doesn&#39;t belong to anybody)

The typical OO behaviour of these two types of Profiles is same but only the  important attributes/properties are common ( the very important ones 5-6 in number), others properties like &quot;interests etc&quot;(almost 10-15 properties) are not there for bot profiles 

The coder who worked on this earlier created separate models/Controllers for bot profiles / User profiles which creates a lot of redundancy everywhere and also as expected hard to maintain, write tests etc.I wanted to DRY this up, atleast to solve some/all of these redundancy problems.

Somebody suggested Single Table Inheritance as a solution 

Somebody suggested Use Polymorphic Associations instead.

what is the better approach. When do we actually use STI?

My own thought was STI is used best when attributes are same for Models and they differ in behaviour.

Thoughts about what can I do?

Single table inheritance and where to use it in Rails

I&#39;m using the excellent JQuery UI to do a &quot;mapping&quot; so the user can &quot;map&quot;
persons from one program to persons from other program.

using this simple JQuery:

    $(document).ready(function() {
        $(&quot;div .draggable&quot;).draggable({
            revert: &#39;valid&#39;,
            snap: false
        });

        $(&quot;div .droppable&quot;).droppable({
            hoverClass: &#39;ui-state-hover&#39;,
            helper: &#39;clone&#39;,
            cursor: &#39;move&#39;,
            drop: function(event, ui) {
                $(this)
                    .addClass(&#39;ui-state-highlight&#39;)
                    .find(&quot;img&quot;)
                    .removeAttr(&quot;src&quot;)
                    .attr(&quot;src&quot;, &quot;_assets/img/icons/check-user-48x48.png&quot;);

                $(this).droppable(&#39;disable&#39;);

                $(ui.draggable)
                    .addClass(&#39;ui-state-highlight&#39;)
                    .find(&quot;img&quot;)
                    .removeAttr(&quot;src&quot;)
                    .attr(&quot;src&quot;, &quot;_assets/img/icons/check-user-48x48.png&quot;);

                $(ui.draggable).draggable(&#39;disable&#39;);
            }
        });

        $(&quot;div .droppable&quot;).bind(&quot;dblclick&quot;, function() {
            $(this)
                .removeClass(&#39;ui-state-highlight&#39;)
                .find(&quot;img&quot;)
                .removeAttr(&quot;src&quot;)
                .attr(&quot;src&quot;, &quot;_assets/img/icons/user-48x48.png&quot;);
            $(this).droppable(&#39;enable&#39;);

            EnableSource($(this));
        });
    });

I get to this:

![alt text][1]

**what I really wanted** was (if possible) create a line between 
**Elsa** and **Kjell** so it makes the connection between them clear.

I can always do it with numbers inside the boxes, but I really 
wanted to know how to do this using the lines.

**Thanks**.

  [1]: http://i.stack.imgur.com/Cyynb.png

How to draw a line between draggable and droppable?

I want to have two foreign keys to the same model:

    class Test(models.model):
        example1 = models.ForeignKey(Example)
        example2 = models.ForeignKey(Example)

I get errors like:

&gt; Accessor for field &#39;example1&#39; clashes with related
&gt; field &#39;Example.test_set&#39;. Add a related_name argument
&gt; to the definition for &#39;example1&#39;.

How can I have two foreign keys to the same model in Django?

I want to have two foreign keys to the same model:
<pre><code class="hljs language-ini">class Test(models.model):
 example1 = models.ForeignKey(Example)
 example2 = models.ForeignKey(Example)
</code></pre>
I get errors like:
> Accessor for field 'example1' clashes with related
> field 'Example.test_set'. Add a related_name argument
> to the definition for 'example1'.

Inspired by the question series &#39;Hidden features of ...&#39;, I am curious to hear about your favorite Django tips or lesser known but useful features you know of.

 - Please, include only one tip per answer.
 - Add Django version requirements if there are any.



Favorite Django Tips &amp; Features?

I&#39;m building a support ticket tracking app and have a few models I&#39;d like to create from one page. Tickets belong to a Customer via a ForeignKey. Notes belong to Tickets via a ForeignKey as well. I&#39;d like to have the option of selecting a Customer (that&#39;s a whole separate project) OR creating a new Customer, then creating a Ticket and finally creating a Note assigned to the new ticket.

Since I&#39;m fairly new to Django, I tend to work iteratively, trying out new features each time. I&#39;ve played with ModelForms but I want to hide some of the fields and do some complex validation. It seems like the level of control I&#39;m looking for either requires formsets or doing everything by hand, complete with a tedious, hand-coded template page, which I&#39;m trying to avoid.

Is there some lovely feature I&#39;m missing? Does someone have a good reference or example for using formsets? I spent a whole weekend on the API docs for them and I&#39;m still clueless. Is it a design issue if I break down and hand-code everything?

Django: multiple models in one template using forms

I&#39;ve been working on a web app using Django, and I&#39;m curious if there is a way to schedule a job to run periodically. 

Basically I just want to run through the database and make some calculations/updates on an automatic, regular basis, but I can&#39;t seem to find any documentation on doing this.

Does anyone know how to set this up?


To clarify:  I know I can set up a `cron` job to do this, but I&#39;m curious if there is some feature in Django that provides this functionality.   I&#39;d like people to be able to deploy this app themselves without having to do much config (preferably zero).

I&#39;ve considered triggering these actions &quot;retroactively&quot; by simply checking if a job should have been run since the last time a request was sent to the site, but I&#39;m hoping for something a bit cleaner.

Set up a scheduled job?

Does somebody know how &quot;modular&quot; is Django? Can I use just the ORM part, to get classes that map to DB tables and know how to read/write from these tables?

If not, what would you recommend as &quot;the Python equivalent of Hibernate&quot;?

Using only the DB part of Django

I wanted a Django model with 2 foreign keys from the same table.  It&#39;s an event table which has 2 columns for employees: the &#39;actor&#39; and the &#39;receiver&#39;. But I get this error: 

&gt; Error: One or more models did not validate: tasks.task: Intermediary
&gt; model TaskEvent has more than one foreign key to Employee, which is
&gt; ambiguous and is not permitted.

Is there a better way to model this?

I think I&#39;m going to add a `TaskEvent_to_Employee` table.  There will be two records in it, one for each of the two employees related to each `TaskEvent`.  Does anyone know an easier workaround?

Django model with 2 foreign keys from the same table

I have a Model as follows:

    class TankJournal(models.Model):
        user = models.ForeignKey(User)
        tank = models.ForeignKey(TankProfile)
        ts = models.IntegerField(max_length=15)
        title = models.CharField(max_length=50)
        body = models.TextField()

I also have a model form for the above model as follows:


    class JournalForm(ModelForm):
        tank = forms.IntegerField(widget=forms.HiddenInput()) 
        
        class Meta:
            model = TankJournal
            exclude = (&#39;user&#39;,&#39;ts&#39;)

I want to know how to set the default value for that tank hidden field. Here is my function to show/save the form so far:

    def addJournal(request, id=0):
        if not request.user.is_authenticated():
            return HttpResponseRedirect(&#39;/&#39;)
    
        # checking if they own the tank
        from django.contrib.auth.models import User
        user = User.objects.get(pk=request.session[&#39;id&#39;])
    
        if request.method == &#39;POST&#39;:
            form = JournalForm(request.POST)
            if form.is_valid():
                obj = form.save(commit=False)
    
                # setting the user and ts
                from time import time
                obj.ts = int(time())
                obj.user = user
    
                obj.tank = TankProfile.objects.get(pk=form.cleaned_data[&#39;tank_id&#39;])
    
                # saving the test
                obj.save()
    
        else:
            form = JournalForm()
    
        try:
            tank = TankProfile.objects.get(user=user, id=id)
        except TankProfile.DoesNotExist:
            return HttpResponseRedirect(&#39;/error/&#39;)

Django set default form values

I query a model:

    Members.objects.all()

And it returns:

    Eric, Salesman, X-Shop
    Freddie, Manager, X2-Shop
    Teddy, Salesman, X2-Shop
    Sean, Manager, X2-Shop

What I want is to know the best Django way to fire
a `group_by` query to my database, like:

    Members.objects.all().group_by(&#39;designation&#39;)

Which doesn&#39;t work, of course.
I know we can do some tricks on `django/db/models/query.py`, but I am just curious to know how to do it without patching.


How to query as GROUP BY in django?

Here is the field declaration in a form: 

    max_number = forms.ChoiceField(widget = forms.Select(), 
        choices = ([(&#39;1&#39;,&#39;1&#39;), (&#39;2&#39;,&#39;2&#39;),(&#39;3&#39;,&#39;3&#39;), ]), initial=&#39;3&#39;, required = True,)
    
I would like to set the initial value to be `3` and this doesn&#39;t seem to work. I have played about with the param, quotes/no quotes, etc... but no change.

Could anyone give me a definitive answer if it is possible? And/or the necessary tweak in my code snippet?

*I am using Django 1.0*

Setting the selected value on a Django forms.ChoiceField

In Django model QuerySets, I see that there is a `__gt` and `__lt` for comparative values, but is there a `__ne` or `!=` (**not equals**)? I want to filter out using a not equals. For example, for

    Model:
        bool a;
        int x;

I want to do

    results = Model.objects.exclude(a=True, x!=5)

The `!=` is not correct syntax. I also tried `__ne`.

I ended up using:

    results = Model.objects.exclude(a=True, x__lt=5).exclude(a=True, x__gt=5)

How do I do a not equal in Django queryset filtering?

I&#39;ve got a set of models that look like this:

    class Page(models.Model):
        title = models.CharField(max_length=255)

    class LinkSection(models.Model):
        page = models.ForeignKey(Page)
        title = models.CharField(max_length=255)

    class Link(models.Model):
        linksection = models.ForeignKey(LinkSection)
        text = models.CharField(max_length=255)
        url = models.URLField()

and an admin.py that looks like this:

    class LinkInline(admin.TabularInline):
        model = Link
    class LinkSectionInline(admin.TabularInline):
        model = LinkSection
        inlines = [ LinkInline, ]
    class PageAdmin(admin.ModelAdmin):
        inlines = [ LinkSectionInline, ]

My goal is to get an admin interface that lets me edit everything on one page. The end result of this model structure is that things are generated into a view+template that looks more or less like:

    &lt;h1&gt;{{page.title}}&lt;/h1&gt;
    {% for ls in page.linksection_set.objects.all %}
    &lt;div&gt;
        &lt;h2&gt;{{ls.title}}&lt;/h2&gt;
        &lt;ul&gt;
             {% for l in ls.link_set.objects.all %}
            &lt;li&gt;&lt;a href=&quot;{{l.url}}&quot;&gt;{{l.title}}&lt;/a&gt;&lt;/li&gt;
             {% endfor %}
        &lt;/ul&gt;
    &lt;/div&gt;
    {% endfor %}

I know that the inline-in-an-inline trick fails in the Django admin, as I expected. Does anyone know of a way to allow this kind of three level model editing? Thanks in advance.

Content Type	Original Author	Original Content on Stackoverflow
Question	MikeN	View Question on Stackoverflow
Solution 1 - Django	strager	View Answer on Stackoverflow
Solution 2 - Django	Matt	View Answer on Stackoverflow
Solution 3 - Django	James Bennett	View Answer on Stackoverflow
Solution 4 - Django	pranjal0819	View Answer on Stackoverflow

How can I have two foreign keys to the same model in Django?

Django Problem Overview

Django Solutions

Solution 1 - Django

Solution 2 - Django

Solution 3 - Django

Solution 4 - Django

How to draw a line between draggable and droppable?

Single table inheritance and where to use it in Rails

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