Author: John Au-Yeung

To fix all records in database have the same value in date field with Python Django, we set the default value to datetime.now or auto_now_add set to True.

For instance, we write

date = models.DateTimeField(auto_now_add=True, blank=True)

or

date = models.DateTimeField(default=datetime.now, blank=True)

to set the created date field to datetime.now() with

default=datetime.now

or

auto_now_add=True

To include related model fields using Django Rest Framework, we can set the depth property in the serializer class.

For instance, we write

class ClassroomSerializer(serializers.ModelSerializer):
    class Meta:
        model = Classroom
        depth = 1

to set the depth field in the Meta class in the ClassroomSerializer to 1 to include the model fields directly related to Classroom.

To set a dynamic File Path in Python Django, we can create a function that returns the file path we want.

For instance, we write

import os

def get_upload_path(instance, filename):
    return os.path.join(
      "user_%d" % instance.owner.id, "car_%s" % instance.slug, filename)

to create the get_upload_path function to return the file path we want given the filename and the model instance.

Then we set that as the upload_to argument of the model field by writing

photo = models.ImageField(upload_to=get_upload_path)

to create the photo ImageField with upload_to set to get_upload_path.

To override a parent model’s attribute with Python Django,. we can create a child model that inherits from the parent.

For instance, we write

class AbstractPlace(models.Model):
    name = models.CharField(max_length=20)
    rating = models.DecimalField()

    class Meta:
        abstract = True

class Place(AbstractPlace):
    pass

class LongNamedRestaurant(AbstractPlace):
    name = models.CharField(max_length=255)
    food_type = models.CharField(max_length=25)

to create the AbstractPlace model which has some fields shared between Place and LongNamedRestaurant.

Then in LongNamedRestaurant, we override the name field from AbstractPlace by setting name to a models.CharField(max_length=255) instead of models.CharField(max_length=20).

To do reverse lookup of foreign keys with Python Django, we can use the filter method.

For instance, we write

def detail(request, venue_id):
    venue = Event.objects.filter(venue__id=venue_id)
    return render(request, 'venue-detail.html', {'venue': venue})

to look up the Event objects by the venue_id with filter.

And then we render the values in the venue-detail.html.