How to generate a query using the IN operator in Django

Django:1.10

In conclusion, it was listed below.

QuerySet API reference | Django documentation | Django https://docs.djangoproject.com/ja/1.10/ref/models/querysets/#in

For queries, you should look at this page.

For example, to generate a query to get a list of books published by the selected author, write:

views.py

def search(request):

    form = SearchForm(request.POST)

    books = None

    if form.is_valid():
        books = Book.objects.filter(author_id__in = form.cleaned_data['author'])

    return render(request, 'books/search.html', {'form': form, 'books': books})

Author, book, genre model.

models.py

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=128)

    def __str__(self):
        return self.name

class Genre(models.Model):
    name = models.CharField(max_length=128)

    def __str__(self):
        return self.name

class Book(models.Model):
    name = models.CharField(max_length=512)
    author =  models.ForeignKey(Author, on_delete=models.CASCADE)
    genres = models.ManyToManyField(Genre)

    def __str__(self):
        return self.name

A form to select an author.

forms.py

from django import forms

from books.models import Author

class SearchForm(forms.Form):

    authors = [(author.id, author.name) for author in Author.objects.all()]

    author = forms.MultipleChoiceField(label='Author', widget=forms.CheckboxSelectMultiple,
            choices=authors, required=False)

If the template is as follows,

searth.html

<form method="post" action="">
    {% csrf_token %}
    <h1>{{ form.author.label }}</h1>
    {{ form.author }}
    <input type="submit" value="Search" />
    <hr />
    <table border="1">
        <tr>
            <th>title</th>
            <th>Author</th>
            <th>Genre</th>
        </tr>
        {% for b in books %}
            <tr>
                <td>{{ b.name }}</td>
                <td>{{ b.author.name }}</td>
                <td>{% for g in b.genres.all %}{{ g.name }}{% endfor %}</td>
            </tr>
        {% endfor %}
    </table>
</form>

It will be displayed like this.

Postscript 2016/11/26

I was implementing the addition of authors, but one problem came up. I get authors from the table to select authors in the above forms.py, but this method seems to be application scope, and even if I add authors, it will not be reflected on the screen unless the server is restarted. I will consider separately what to do when assigning transaction data to choices.

Postscript 2017/01/05

The above problem has been solved.

Choices not updated in Django's Multiple Choice Field http://qiita.com/nakkun/items/26598a7bf1f80b215ff2

Maybe this should be fine. .. ..