Re: How do I use mathematical calculations on my forloop Article/Publication list?

Take a look at the docs for aggregation and annotation and using F expressions in them. I just skimmed over your email, but there might be something useful to learn there.

https://docs.djangoproject.com/en/dev/topics/db/aggregation/

https://docs.djangoproject.com/en/dev/ref/models/queries/#f-expressions

Also, is there a reason why you're not using class based views?

https://docs.djangoproject.com/en/dev/topics/class-based-views/

Cheers,

AT

On Sat, Nov 23, 2013 at 8:12 PM, Pepsodent Cola <pepsodentcola@gmail.com> wrote:

I worked some more on James' hint:  articles[0].num_publications() 

And I followed some tutorial exercises on making Template filters.  After seeing DJ-Tom's hint.

And this is as far as I got from trying things...

I'm trying to send two lists to my template so I can do some parallel iteration in my forloop.

But then I realized that type(articles) is a Queryset and not a list so I can't use zip() like in the examples I'm reading.

So how can I integrate my list

    publicists_coverage = [] # List 3

into this forloop template code?

    {% for row in articles %}

#_______________________________________________________________________________

def index(request):

    publications = Publication.objects.all()

    # sum_publications = Publication.objects.filter(article__pk=1).count()

    # List 1

    articles = Article.objects.all().annotate(num_publications=Count('publications'))

    #>>> type(articles)

    #<class 'django.db.models.query.QuerySet'>

    # 3

    publication_per_article = [] # List 2

    for i in range(articles.count()):

        x = articles[i].num_publications

        publication_per_article.append(x)

    # 5

    total_publicists = Publication.objects.all().count()

    # Calculate things!

    publicists_coverage = [] # List 3

    for row in publication_per_article:

        y = float(row)/total_publicists

        publicists_coverage.append(y)

    ziplist = zip(articles, publicists_coverage)

    context = {'publications':publications, 'articles':articles,

               'total_publicists':total_publicists, 'ziplist':ziplist}

#    context = {'publications':publications,

#               'total_publicists':total_publicists, 'ziplist':ziplist}

    return render(request, 'magazine/index.html', context)

#_______________________________________________________________________________

{% if articles and ziplist %}

    <table border="1">

    <tr>

        <th>Article id</th>

        <th>Article</th>

        <th>Publication</th>

        <th>Publicists coverage (%)</th>

    </tr>

    {% for row in articles %}

    <tr>

        <td>{{ row.id }}</td>

        <td>{{ row.headline }}</td>

        <td>{{ row.num_publications }}</td>

        <td>({{ row.num_publications }} / {{ total_publicists }}) = {{ publicists_coverage }}x %</td>

    </tr>

    {% endfor %}

    </table>

{% else %}

    <p>No Articles or Ziplist are available.</p>

{% endif %}

On Wednesday, November 20, 2013 10:29:24 PM UTC+1, Pepsodent Cola wrote:

1.)

How do I use mathematical calculations on my forloop Article/Publication list?

* I have attached a screenshot with the table field that I'm working on "Publicists coverage (%)".

* Admin user/pass = joe/joe

* I have also attached my project files so that you can see things for yourselves.

2.)

Is the solution I'm working with in "Index View page" the correct practice to do my mathematical calculations?

#_______________________________________________________________________________

def index(request):

    publications = Publication.objects.all()

    # sum_publications = Publication.objects.filter(article__pk=1).count()

    articles = Article.objects.all().annotate(num_publications=Count('publications'))

    #articles_int = int(articles)

    sum_publicists = Publication.objects.all().count()

    #publicists_coverage = articles/sum_publicists

#    context = {'publications':publications, 'sum_publicists':sum_publicists,

#               'publicists_coverage':publicists_coverage, 'articles':articles}

    context = {'publications':publications, 'sum_publicists':sum_publicists,

               'articles':articles}

    return render(request, 'magazine/index.html', context)

#_______________________________________________________________________________

<article>

    <h1>How many Publications was each Article in?</h1>

{% if articles %}

    <table border="1">

    <tr>

        <th>Article id</th>

        <th>Article</th>

        <th>Publication</th>

        <th>Publicists coverage (%)</th>

    </tr>

    {% for row in articles %}

    <tr>

        <td>{{ row.id }}</td>

        <td>{{ row.headline }}</td>

        <td>{{ row.num_publications }}</td>

        <td>({{ row.num_publications }} / {{ sum_publicists }}) = x %</td>

    </tr>

    {% endfor %}

    </table>

{% else %}

    <p>No Articles are available.</p>

{% endif %}

    <hr>

</article>

#_______________________________________________________________________________

3.)

When I try to convert articles object into int it doesn't work.  Am I going the wrong direction when thinking about solving things like this?

Exception Type: TypeError

Exception Value: int() argument must be a string or a number, not 'QuerySet'

Exception Location: /home/linux/Django/ManyToMany/magazine/views.py in index, line 17

>>> articles = Article.objects.all().annotate(num_publications=Count('publications'))

>>> type(articles)

<class 'django.db.models.query.QuerySet'>

>>> 

>>> articles_int = int(articles)

Traceback (most recent call last):

  File "<console>", line 1, in <module>

TypeError: int() argument must be a string or a number, not 'QuerySet'

>>> 

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