try using [exclude][1] 

    Table.objects.exclude(title__in=myListOfTitles)


  [1]: https://docs.djangoproject.com/en/dev/topics/db/queries/#retrieving-specific-objects-with-filters

    Table.objects.exclude(title__in=myListOfTitles)

(this thread is old but still could be googled)

you can use `models.Q` with &quot;~&quot; as follows:
```
Table.objects.filter(~Q(title__in=myListOfTitles))
```
this method specially is helpful when you have multiple conditions.

**Django provides two options.**

    exclude(&lt;condition&gt;)
    filter(~Q(&lt;condition&gt;))

Method 2 using Q() method

    &gt;&gt;&gt; from django.db.models import Q
    &gt;&gt;&gt; queryset = User.objects.filter(~Q(id__lt=5))

I&#39;m having a hard time finding examples for rotating an image around a specific point by a specific (often very small) angle in Python using OpenCV.

This is what I have so far, but it produces a very strange resulting image, but it is rotated somewhat:

    def rotateImage( image, angle ):
        if image != None:
            dst_image = cv.CloneImage( image )

            rotate_around = (0,0)
            transl = cv.CreateMat(2, 3, cv.CV_32FC1 )

            matrix = cv.GetRotationMatrix2D( rotate_around, angle, 1.0, transl )
            cv.GetQuadrangleSubPix( image, dst_image, transl )
            cv.GetRectSubPix( dst_image, image, rotate_around )

        return dst_image


OpenCV Python rotate image by X degrees around specific point

I know the size of a vector, which is the best way to initialize it?

**Option 1:**

    vector&lt;int&gt; vec(3); //in .h
    vec.at(0)=var1;     //in .cpp
    vec.at(1)=var2;     //in .cpp
    vec.at(2)=var3;     //in .cpp

**Option 2:**

    vector&lt;int&gt; vec;     //in .h
    vec.reserve(3);      //in .cpp
    vec.push_back(var1); //in .cpp
    vec.push_back(var2); //in .cpp
    vec.push_back(var3); //in .cpp

I guess, Option2 is better than Option1. Is it? Any other options?

Vector: initialization or reserve?

I have a very simple query: `select * from tbl1 where title not in(&#39;asdasd&#39;, &#39;asdasd&#39;)`. 

How do I translate that to Django? It&#39;s like I want the opposite of: `Table.objects.filter(title__in=myListOfTitles)`


Django equivalent of SQL not in

<p>I have a very simple query: <code>select * from tbl1 where title not in('asdasd', 'asdasd')</code>.</p>
<p>How do I translate that to Django? It's like I want the opposite of: <code>Table.objects.filter(title__in=myListOfTitles)</code></p>


I often see people claiming their backend is implemented in Django, but isn&#39;t Django supposed to be for the frontend? I&#39;d assume the backend refers to the business logic where the frontend refers to the presentation. Am I missing something?



Is Django for the frontend or backend?

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&#39;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 its implemented in the admin interface.

Delete multiple objects in django

I&#39;ve tried prefetch_related() in django 1.4 from trunk and can&#39;t make it to prefetch reverse lookup.

My simplified models (each book has many prices):

    class Book(models.Model):
        # some fields
    
    class Price(models.Model):
        book = models.ForeignKey(Book)


My view&#39;s query:
    
    books = Book.objects.prefetch_related(&#39;price&#39;)
    
Then, I got the AttributeError message:
    
    AttributeError: Cannot find &#39;price&#39; on Book object, &#39;price&#39; is an invalid parameter to prefetch_related()


How to make it work?
Thanks.


Django: Does prefetch_related() follow reverse relationship lookup?

This is related to this question: https://stackoverflow.com/questions/9260249/django-return-json-and-html-depending-on-client-python

----------


I have a command line Python API for a Django app. When I access the app through the API it should return JSON and with a browser it should return HTML. I can use different URLs to access the different versions but how do I render the HTML template and JSON in the **views.py** with just one template?

To render the HTML I would use:

    return render_to_response(&#39;sample/sample.html....&#39;)

But how would I do the same for JSON without putting a JSON template? (the `content-type` should be `application/json` instead of `text/html`)

What would determine the JSON and HTML outputs?

So in my **views.py**:

    if something:
        return render_to_response(&#39;html_template&#39;,.....)
    else:
        return HttpReponse(jsondata,mimetype=&#39;application/json&#39;)


How do I return JSON without using a template in Django?

I&#39;m sure this is a trivial operation, but I can&#39;t figure out how it&#39;s done.

There&#39;s got to be something smarter than this:

    ids = [1, 3, 6, 7, 9]

    for id in ids:
        MyModel.objects.filter(pk=id)

I&#39;m looking to get them all in one query with something like:

    MyModel.objects.filter(pk=[1, 3, 6, 7, 9])

How can I filter a Django query with a list of values?

How can I filter a Django query with a list of values?

I want to do pretty much the same like in [this ticket at djangoproject.com][1], but with some additonal formatting. From this query

    &gt;&gt;&gt; MyModel.objects.values(&#39;cryptic_value_name&#39;)
    [{&#39;cryptic_value_name&#39;: 1}, {&#39;cryptic_value_name&#39;: 2}]

I want to get something like that:

    &gt;&gt;&gt; MyModel.objects.values(renamed_value=&#39;cryptic_value_name&#39;)
    [{&#39;renamed_value&#39;: 1}, {&#39;renamed_value&#39;: 2}]

Is there another, more builtin way or do I have to do this manually?

  [1]: https://code.djangoproject.com/ticket/12222

How to rename items in values() in Django?

I have a model something like this:

```python
class Task(models.Model):
    progress = models.PositiveIntegerField()
    estimated_days = models.PositiveIntegerField()
```

Now I would like to do a calculation `Sum(progress * estimated_days)` on the database level. Using Django Aggregation I can have the sum for each field but not the summation of multiplication of fields. 

Django Aggregation: Summation of Multiplication of two fields

I have two models like this:

    class User(models.Model):
        email = models.EmailField()
    
    class Report(models.Model):
        user = models.ForeignKey(User)

In reality each model has more fields which are of no consequence to this question.

I want to filter all users who have an email which starts with &#39;a&#39; and have no reports. There will be more `.filter()` and `.exclude()` criteria based on other fields.

I want to approach it like this:

    users = User.objects.filter(email__like = &#39;a%&#39;)
    
    users = users.filter(&lt;other filters&gt;)
    
    users = ???

I would like ??? to filter out users who do not have reports associated with them. How would I do this? If this is not possible as I have presented it, what is an alternate approach?

In a Django QuerySet, how to filter for &quot;not exists&quot; in a many-to-one relationship

I&#39;m kind of new to webapps and database stuff in general so this might be a dumb question. I want to make a model (&quot;CategoryModel&quot;) with a field that points to the primary id of another instance of the model (its parent).

    class CategoryModel(models.Model):
        parent = models.ForeignKey(CategoryModel)

How do I do this? Thanks! 

Django self-referential foreign key

I&#39;ve been doing a lot of research lately into using Pyramid with SQLAlchemy versus keeping a current application in Django.  That by itself is an entire debate, but I&#39;m not here to discuss that.

What I do want to know is, why is SQLAlchemy universally considered better than Django ORM?  Almost every, if not every, comparison I&#39;ve found between the two favors SQLAlchemy.  I assume performance is a big one, as the structure of SQLAlchemy lets it translate to SQL much more smoothly.

But, I&#39;ve also heard that with harder tasks, Django ORM is nearly impossible to use.  I want to scope out how huge of an issue this can be.  I&#39;ve been reading one of the reasons to switch to SQLAlchemy is when Django ORM is no longer suiting your needs.

So, in short, could someone provide a query (doesn&#39;t have to be actual SQL syntax) that SQLAlchemy can do, but Django ORM cannot possibly do without adding in additional raw SQL?

**Update**:

I&#39;ve been noticing this question getting quite some attention since I first asked, so I&#39;d like to throw in my extra two cents.

In the end we ended up using SQLAlchemy and I must say I&#39;m happy with the decision.

I&#39;m revisiting this question to provide an additional feature of SQLAlchemy that, so far, I&#39;ve not been able to replicate in Django ORM.  If someone can provide an example of how to do this I&#39;ll gladly eat my words.

Let&#39;s say you want to use some postgresql function, such as similarity(), which provides a fuzzy comparison (see: https://stackoverflow.com/questions/11249635/finding-similar-strings-with-postgresql-quickly - tl;dr input two strings get back a percent similarity).

I&#39;ve done some searching on how to do this using the Django ORM and have found nothing other than using raw sql as seems to be apparent from their documentation: https://docs.djangoproject.com/en/dev/topics/db/sql/.

i.e.

    Model.objects.raw(&#39;SELECT * FROM app_model ORDER BY \
    similarity(name, %s) DESC;&#39;, [input_name])

SQLalchemy, however, has func(), as described here: http://docs.sqlalchemy.org/en/latest/core/sqlelement.html#sqlalchemy.sql.expression.func

    from sqlalchemy import desc, func
    session.query(Model).order_by(func.similarity(Model.name, input_name))

This allows you to generate sql for any defined sql/postgresql/etc function and not require raw sql.

Content Type	Original Author	Original Content on Stackoverflow
Question	Ali	View Question on Stackoverflow
Solution 1 - Django	JamesO	View Answer on Stackoverflow
Solution 2 - Django	Alexey Savanovich	View Answer on Stackoverflow
Solution 3 - Django	omid	View Answer on Stackoverflow
Solution 4 - Django	Muhammad Abdullah	View Answer on Stackoverflow

Django equivalent of SQL not in

Django Problem Overview

Django Solutions

Solution 1 - Django

Solution 2 - Django

Solution 3 - Django

Solution 4 - Django

Vector: initialization or reserve?

OpenCV Python rotate image by X degrees around specific point

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