Topic guide Making queries Retrieving objects

Field lookups are how you specify the meat of an SQL WHERE clause. They’re specified as keyword arguments to the QuerySet methods filter(), exclude() and get(). Basic lookups keyword arguments take the form field__lookuptype=value. (That’s a double-underscore).

Topic guide Making queries Retrieving objects

… equivalent: The use of pk isn’t limited to __exact queries – any query term can be combined with pk to perform a query on the primary key of a model: pk lookups also work across joins. For example, these three …

Topic guide Making queries Querying JSONField

… based on a given dictionary key, use that key as the lookup name: Multiple keys can be chained together to form a path lookup: If the key is an integer, it will be interpreted as an index transform in an …

Topic guide Formsets

Initial data is what drives the main usability of a formset. As shown above you can define the number of extra forms.

Topic guide Formsets

The absolute_max parameter to formset_factory() allows limiting the number of forms that can be instantiated when supplying POST data. This protects against memory exhaustion attacks using forged POST requests: When absolute_max is None, it defaults to max_num + 1000.

Topic guide Formsets Dealing with ordering and deletion of forms

BaseFormSet.can_order Default: False Lets you create a formset with the ability to order: This adds an additional field to each form. This new field is named ORDER and is an forms.IntegerField.

Topic guide Formsets Dealing with ordering and deletion of forms

BaseFormSet.can_delete Default: False Lets you create a formset with the ability to select forms for deletion: Similar to can_order this adds a new field to each form named DELETE and is a forms.BooleanField.

Topic guide Formsets Dealing with ordering and deletion of forms

If you call formset.save(commit=False), objects will not be deleted automatically.

Topic guide Formsets

If you need to add additional fields to the formset this can be easily accomplished. The formset base class provides an add_fields method.

Topic guide Formsets

BaseFormSet.as_p() : Renders the formset with the template_name_p template. BaseFormSet.as_table() : Renders the formset with the template_name_table template. BaseFormSet.as_ul() : Renders the formset with the template_name_ul template.

Topic guide Working with forms Forms in Django

… the database, for example) pass it to the template context expand it to HTML markup using template variables Rendering a form in a template involves nearly the same work as rendering any other kind of object, but there are some …

Topic guide Creating forms from models

classModelForm[source] If you’re building a database-driven app, chances are you’ll have forms that map closely to Django models. For instance, you might have a BlogComment model, and you want to create a form that lets people submit comments.

Topic guide Creating forms from models ModelForm

As you might expect, the ForeignKey and ManyToManyField model field types are special cases: ForeignKey is represented by django.forms.ModelChoiceField, which is a ChoiceField whose choices are a model QuerySet.

Topic guide Creating forms from models ModelForm

Consider this set of models: With these models, the ModelForm subclasses above would be roughly equivalent to this (the only difference being the save() method, which we’ll discuss in a moment.):

Topic guide Creating forms from models ModelForm

You can create forms from a given model using the standalone function modelform_factory(), instead of using a class definition.

Topic guide Creating forms from models

classmodels.BaseModelFormSet Like regular formsets, Django provides a couple of enhanced formset classes to make working with Django models more convenient. Let’s reuse the Author model from above: Using fields restricts the formset to use only the given fields.

Topic guide Creating forms from models Model formsets

As with a ModelForm, you can save the data as a model object. This is done with the formset’s save() method: The save() method returns the instances that have been saved to the database.

Topic guide Creating forms from models Model formsets

There are three ways to render a formset in a Django template.

Topic guide File Uploads Basic file uploads

If you’re saving a file on a Model with a FileField, using a ModelForm makes this process much easier.

Topic guide How to use sessions

As a convenience, Django provides a way to test whether the user’s browser accepts cookies. Call the set_test_cookie() method of request.session in a view, and call test_cookie_worked() in a subsequent view – not in the same view call.