getting_started.rst

Getting started

For example purposes, we'll use a simplified book app. Here is our core.models.py:

class Author(models.Model):
    name = models.CharField(max_length=100)

    def __unicode__(self):
        return self.name


class Category(models.Model):
    name = models.CharField(max_length=100)

    def __unicode__(self):
        return self.name


class Book(models.Model):
    name = models.CharField('Book name', max_length=100)
    author = models.ForeignKey(Author, blank=True, null=True)
    author_email = models.EmailField('Author email', max_length=75, blank=True)
    imported = models.BooleanField(default=False)
    published = models.DateField('Published', blank=True, null=True)
    price = models.DecimalField(max_digits=10, decimal_places=2, null=True,
            blank=True)
    categories = models.ManyToManyField(Category, blank=True)

    def __unicode__(self):
        return self.name

Creating import-export resource

To integrate django-import-export with Book model, we will create a resource class in admin.py that will describe how this resource can be imported or exported.

from import_export import resources
from core.models import Book


class BookResource(resources.ModelResource):

    class Meta:
        model = Book

Exporting data

Now that we have defined a resource class, we can export books:

>>> dataset = BookResource().export()
>>> print dataset.csv
id,name,author,author_email,imported,published,price,categories
2,Some book,1,,0,2012-12-05,8.85,1

Customize resource options

By default ModelResource introspects model fields and creates import_export.fields.Field attributes with an appropriate widget for each field.

To affect which model fields will be included in an import-export resource, use the fields option to whitelist fields:

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        fields = ('id', 'name', 'price',)

Or the exclude option to blacklist fields:

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        exclude = ('imported', )

An explicit order for exporting fields can be set using the export_order option:

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        fields = ('id', 'name', 'author', 'price',)
        export_order = ('id', 'price', 'author', 'name')

The default field for object identification is id, you can optionally set which fields are used as the id when importing:

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        import_id_fields = ('isbn',)
        fields = ('isbn', 'name', 'author', 'price',)

When defining ModelResource fields it is possible to follow model relationships:

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        fields = ('author__name',)

Note

Following relationship fields sets field as readonly, meaning this field will be skipped when importing data.

By default all records will be imported, even if no changes are detected. This can be changed setting the skip_unchanged option. Also, the report_skipped option controls whether skipped records appear in the import Result object, and if using the admin whether skipped records will show in the import preview page:

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        skip_unchanged = True
        report_skipped = False
        fields = ('id', 'name', 'price',)

.. seealso::

    :doc:`/api_resources`

Declaring fields

It is possible to override a resource field to change some of its options:

from import_export import fields

class BookResource(resources.ModelResource):
    published = fields.Field(column_name='published_date')

    class Meta:
        model = Book

Other fields that don't exist in the target model may be added:

from import_export import fields

class BookResource(resources.ModelResource):
    myfield = fields.Field(column_name='myfield')

    class Meta:
        model = Book

.. seealso::

    :doc:`/api_fields`
        Available field types and options.

Advanced data manipulation

Not all data can be easily extracted from an object/model attribute. In order to turn complicated data model into a (generally simpler) processed data structure, dehydrate_<fieldname> method should be defined:

from import_export import fields

class BookResource(resources.ModelResource):
    full_title = fields.Field()

    class Meta:
        model = Book

    def dehydrate_full_title(self, book):
        return '%s by %s' % (book.name, book.author.name)

Customize widgets

ModelResource creates a field with a default widget for a given field type. If the widget should be initialized with different arguments, set the widgets dict.

In this example widget, the published field is overriden to use a different date format. This format will be used both for importing and exporting resource.

class BookResource(resources.ModelResource):

    class Meta:
        model = Book
        widgets = {
                'published': {'format': '%d.%m.%Y'},
                }

.. seealso::

    :doc:`/api_widgets`
        available widget types and options.

Importing data

Let's import data:

>>> import tablib
>>> from import_export import resources
>>> from core.models import Book
>>> book_resource = resources.modelresource_factory(model=Book)()
>>> dataset = tablib.Dataset(['', 'New book'], headers=['id', 'name'])
>>> result = book_resource.import_data(dataset, dry_run=True)
>>> print result.has_errors()
False
>>> result = book_resource.import_data(dataset, dry_run=False)

In 4th line we use modelresource_factory to create a default ModelResource. ModelResource class created this way is equal as in :ref:`base-modelresource`.

In 5th line a Dataset with subset of Book fields is created.

In rest of code we first pretend to import data with dry_run set, then check for any errors and import data.

.. seealso::

    :doc:`/import_workflow`
        for detailed import workflow descripton and customization options.

Deleting data

To delete objects during import, implement for_delete method on resource class.

Example resource with delete field:

class BookResource(resources.ModelResource):
    delete = fields.Field(widget=widgets.BooleanWidget())

    def for_delete(self, row, instance):
        return self.fields['delete'].clean(row)

    class Meta:
        model = Book

Import of this resource will delete model instances for rows that have column delete set to 1.

Admin integration

Admin integration is achieved by subclassing (in admin.py) ImportExportModelAdmin or one of the available mixins (ImportMixin, ExportMixin, or ImportExportMixin):

from import_export.admin import ImportExportModelAdmin


class BookAdmin(ImportExportModelAdmin):
    resource_class = BookResource
    pass

A screenshot of the change view with Import and Export buttons.

A screenshot of the import view.

A screenshot of the confirm import view.

Another approach to exporting data is by subclassing ImportExportActionModelAdmin which implements export as an admin action. As a result it's possible to export a list of objects selected on the change list page:

from import_export.admin import ImportExportActionModelAdmin


class BookAdmin(ImportExportActionModelAdmin):
    resource_class = BookResource
    pass

A screenshot of the change view with Import and Export as an admin action.

.. seealso::

    :doc:`/api_admin`
        available mixins and options.