DjangoItem

DjangoItem is a class of item that gets its fields definition from a Django model, you simply create a DjangoItem and specify what Django model it relates to.

Besides of getting the model fields defined on your item, DjangoItem provides a method to create and populate a Django model instance with the item data.

Using DjangoItem

DjangoItem works much like ModelForms in Django, you create a subclass and define its django_model attribute to be a valid Django model. With this you will get an item with a field for each Django model field.

In addition, you can define fields that aren’t present in the model and even override fields that are present in the model defining them in the item.

Let’s see some examples:

Django model for the examples:

class Person(models.Model):
    name = models.CharField(max_length=255)
    age = models.IntegerField()

Defining a basic DjangoItem:

class PersonItem(DjangoItem):
    django_model = Person

DjangoItem work just like Item:

p = PersonItem()
p['name'] = 'John'
p['age'] = '22'

To obtain the Django model from the item, we call the extra method save() of the DjangoItem:

>>> person = p.save()
>>> person.name
'John'
>>> person.age
'22'
>>> person.id
1

As you see the model is already saved when we call save(), we can prevent this by calling it with commit=False. We can use commit=False in save() method to obtain an unsaved model:

>>> person = p.save(commit=False)
>>> person.name
'John'
>>> person.age
'22'
>>> person.id
None

As said before, we can add other fields to the item:

class PersonItem(DjangoItem):
    django_model = Person
    sex = Field()

p = PersonItem()
p['name'] = 'John'
p['age'] = '22'
p['sex'] = 'M'

Note

fields added to the item won’t be taken into account when doing a save()

And we can override the fields of the model with your own:

class PersonItem(DjangoItem):
    django_model = Person
    name = Field(default='No Name')

This is useful to provide properties to the field, like a default or any other property that your project uses.

DjangoItem caveats

DjangoItem is a rather convenient way to integrate Scrapy projects with Django models, but bear in mind that Django ORM may not scale well if you scrape a lot of items (ie. millions) with Scrapy. This is because a relational backend is often not a good choice for a write intensive application (such as a web crawler), specially if the database is highly normalized and with many indices.