Author: John Au-Yeung

To retrieve a Foreign Key value with Python django-rest-framework serializers, we add the foreign key field into our serialize and put the field in the tuple list in the Meta class.

For instance, we write

class ItemSerializer(serializers.ModelSerializer):
    category_name = serializers.CharField(source='category.name')

    class Meta:
        model = Item
        fields = ('id', 'name', 'category_name')

to add the ItemSerializer that has the category_name field set to a CharField that has source set to the category.name column.

And then in the Meta class, we have fields set to a tuple with the category_name` field in it to return it.

To upload multiple images to a blog post in Python Django, we add a model for the images.

For instance, we write

from django.db import models
from django.contrib.auth.models import User
from django.template.defaultfilters import slugify

class Post(models.Model):
    user = models.ForeignKey(User)
    title = models.CharField(max_length=128)
    body = models.CharField(max_length=400)
  
def get_image_filename(instance, filename):
    title = instance.post.title
    slug = slugify(title)
    return "post_images/%s-%s" % (slug, filename)  


class Images(models.Model):
    post = models.ForeignKey(Post, default=None)
    image = models.ImageField(upload_to=get_image_filename,
                              verbose_name='Image')

to create the Post and Images models.

And then we reference the post with the image in the Images model.

And we have the image file field.

We use the get_image_filename function to get the image path to save the image file to.

To get list of model fields with Python Django, we use MyModel._meta.get_fields().

For instance, we write

[f.name for f in MyModel._meta.get_fields()]

to get all the fields with MyModel._meta.get_fields().

Then we get the name of each field with f.name.

To perform Python Django database migrations when using Docker-Compose, we can add the migrate command in a script.

For instance, in docker-entrypoint.sh, we add

python manage.py collectstatic --noinput
python manage.py migrate
python manage.py runserver 0.0.0.0:8000

to collect static files with

python manage.py collectstatic --noinput

We run the database migrations with

python manage.py migrate

And then we start the server with

python manage.py runserver 0.0.0.0:8000

Then we run the script during docker-compose by running the script with a command by putting it in the command property.

To filter a Python Django query with a list of values, we can use the filter method with in.

For instance, we write

Blog.objects.filter(pk__in=[1, 4, 7])

to search Blog entries with pk set to 1,4 or 7 by calling Blog.objects.filter with the pk_in argument set to [1, 4, 7].