ModelFormLink to this heading#If you’re building a database-driven app, chances are you’ll have forms that\nmap closely to Django models. For instance, you might have a BlogComment\nmodel, and you want to create a form that lets people submit comments. In this\ncase, it would be redundant to define the field types in your form, because\nyou’ve already defined the fields in your model.
For this reason, Django provides a helper class that lets you create a Form\nclass from a Django model.
Por ejemplo:
\n>>> from django.forms import ModelForm\n>>> from myapp.models import Article\n\n# Create the form class.\n>>> class ArticleForm(ModelForm):\n... class Meta:\n... model = Article\n... fields = ["pub_date", "headline", "content", "reporter"]\n...\n\n# Creating a form to add an article.\n>>> form = ArticleForm()\n\n# Creating a form to change an existing article.\n>>> article = Article.objects.get(pk=1)\n>>> form = ArticleForm(instance=article)\nThe generated Form class will have a form field for every model field\nspecified, in the order specified in the fields attribute.
Each model field has a corresponding default form field. For example, a\nCharField on a model is represented as a CharField on a form. A model\nManyToManyField is represented as a MultipleChoiceField. Here is the\nfull list of conversions:
Model field | \nForm field | \n
|---|---|
| \n | Not represented in the form | \n
| \n | Not represented in the form | \n
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| \n | Not represented in the form | \n
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As you might expect, the ForeignKey and ManyToManyField model field\ntypes are special cases:
ForeignKey is represented by django.forms.ModelChoiceField,\nwhich is a ChoiceField whose choices are a model QuerySet.
ManyToManyField is represented by\ndjango.forms.ModelMultipleChoiceField, which is a\nMultipleChoiceField whose choices are a model QuerySet.
In addition, each generated form field has attributes set as follows:
\nIf the model field has blank=True, then required is set to\nFalse on the form field. Otherwise, required=True.
The form field’s label is set to the verbose_name of the model\nfield, with the first character capitalized.
The form field’s help_text is set to the help_text of the model\nfield.
If the model field has choices set, then the form field’s widget\nwill be set to Select, with choices coming from the model field’s\nchoices. The choices will normally include the blank choice which is\nselected by default. If the field is required, this forces the user to\nmake a selection. The blank choice will not be included if the model\nfield has blank=False and an explicit default value (the\ndefault value will be initially selected instead).
Finally, note that you can override the form field used for a given model\nfield. See Overriding the default fields below.
\nConsider this set of models:
\nfrom django.db import models\nfrom django.forms import ModelForm\n\nTITLE_CHOICES = {\n "MR": "Mr.",\n "MRS": "Mrs.",\n "MS": "Ms.",\n}\n\n\nclass Author(models.Model):\n name = models.CharField(max_length=100)\n title = models.CharField(max_length=3, choices=TITLE_CHOICES)\n birth_date = models.DateField(blank=True, null=True)\n\n def __str__(self):\n return self.name\n\n\nclass Book(models.Model):\n name = models.CharField(max_length=100)\n authors = models.ManyToManyField(Author)\n\n\nclass AuthorForm(ModelForm):\n class Meta:\n model = Author\n fields = ["name", "title", "birth_date"]\n\n\nclass BookForm(ModelForm):\n class Meta:\n model = Book\n fields = ["name", "authors"]\nWith these models, the ModelForm subclasses above would be roughly\nequivalent to this (the only difference being the save() method, which\nwe’ll discuss in a moment.):
from django import forms\n\n\nclass AuthorForm(forms.Form):\n name = forms.CharField(max_length=100)\n title = forms.CharField(\n max_length=3,\n widget=forms.Select(choices=TITLE_CHOICES),\n )\n birth_date = forms.DateField(required=False)\n\n\nclass BookForm(forms.Form):\n name = forms.CharField(max_length=100)\n authors = forms.ModelMultipleChoiceField(queryset=Author.objects.all())\nModelFormLink to this heading#There are two main steps involved in validating a ModelForm:
Just like normal form validation, model form validation is triggered implicitly\nwhen calling is_valid() or accessing the\nerrors attribute and explicitly when calling\nfull_clean(), although you will typically not use the latter method in\npractice.
Model validation is triggered from within the form validation step right\nafter the form’s clean() method is called. First, the model’s\nfull_clean() is called with\nvalidate_unique=False and validate_constraints=False, then the model’s\nvalidate_unique() and\nvalidate_constraints() methods are called in\norder.
clean() methodLink to this heading#You can override the clean() method on a model form to provide additional\nvalidation in the same way you can on a normal form.
A model form instance attached to a model object will contain an instance\nattribute that gives its methods access to that specific model instance.
As part of the validation process, ModelForm will call the clean()\nmethod of each field on your model that has a corresponding field on your form.\nIf you have excluded any model fields, validation will not be run on those\nfields. See the form validation documentation\nfor more on how field cleaning and validation work.
The model’s clean() method will be called before any uniqueness or\nconstraint checks are made. See Validating objects\nfor more information on the model’s clean() hook.
error_messagesLink to this heading#Error messages defined at the\nform field level or at the\nform Meta level always take\nprecedence over the error messages defined at the\nmodel field level.
Error messages defined on model fields are only used when the\nValidationError is raised during the model validation step and no corresponding error messages are defined at\nthe form level.
You can override the error messages from NON_FIELD_ERRORS raised by model\nvalidation by adding the NON_FIELD_ERRORS key\nto the error_messages dictionary of the ModelForm’s inner Meta\nclass:
from django.core.exceptions import NON_FIELD_ERRORS\nfrom django.forms import ModelForm\n\n\nclass ArticleForm(ModelForm):\n class Meta:\n error_messages = {\n NON_FIELD_ERRORS: {\n "unique_together": "%(model_name)s's %(field_labels)s are not unique.",\n }\n }\nsave() methodLink to this heading#Every ModelForm also has a save() method. This method creates and saves\na database object from the data bound to the form. A subclass of ModelForm\ncan accept an existing model instance as the keyword argument instance; if\nthis is supplied, save() will update that instance. If it’s not supplied,\nsave() will create a new instance of the specified model:
>>> from myapp.models import Article\n>>> from myapp.forms import ArticleForm\n\n# Create a form instance from POST data.\n>>> f = ArticleForm(request.POST)\n\n# Save a new Article object from the form's data.\n>>> new_article = f.save()\n\n# Create a form to edit an existing Article, but use\n# POST data to populate the form.\n>>> a = Article.objects.get(pk=1)\n>>> f = ArticleForm(request.POST, instance=a)\n>>> f.save()\nNote that if the form hasn’t been validated, calling save() will do so by checking\nform.errors. A ValueError will be raised if the data in the form\ndoesn’t validate – i.e., if form.errors evaluates to True.
If an optional field doesn’t appear in the form’s data, the resulting model\ninstance uses the model field default, if\nthere is one, for that field. This behavior doesn’t apply to fields that use\nCheckboxInput,\nCheckboxSelectMultiple, or\nSelectMultiple (or any custom widget whose\nvalue_omitted_from_data() method always returns\nFalse) since an unchecked checkbox and unselected <select multiple>\ndon’t appear in the data of an HTML form submission. Use a custom form field or\nwidget if you’re designing an API and want the default fallback behavior for a\nfield that uses one of these widgets.
This save() method accepts an optional commit keyword argument, which\naccepts either True or False. If you call save() with\ncommit=False, then it will return an object that hasn’t yet been saved to\nthe database. In this case, it’s up to you to call save() on the resulting\nmodel instance. This is useful if you want to do custom processing on the\nobject before saving it, or if you want to use one of the specialized\nmodel saving options. commit is True\nby default.
Another side effect of using commit=False is seen when your model has\na many-to-many relation with another model. If your model has a many-to-many\nrelation and you specify commit=False when you save a form, Django cannot\nimmediately save the form data for the many-to-many relation. This is because\nit isn’t possible to save many-to-many data for an instance until the instance\nexists in the database.
To work around this problem, every time you save a form using commit=False,\nDjango adds a save_m2m() method to your ModelForm subclass. After\nyou’ve manually saved the instance produced by the form, you can invoke\nsave_m2m() to save the many-to-many form data. For example:
# Create a form instance with POST data.\n>>> f = AuthorForm(request.POST)\n\n# Create, but don't save the new author instance.\n>>> new_author = f.save(commit=False)\n\n# Modify the author in some way.\n>>> new_author.some_field = "some_value"\n\n# Save the new instance.\n>>> new_author.save()\n\n# Now, save the many-to-many data for the form.\n>>> f.save_m2m()\nCalling save_m2m() is only required if you use save(commit=False).\nWhen you use a save() on a form, all data – including many-to-many data –\nis saved without the need for any additional method calls. For example:
# Create a form instance with POST data.\n>>> a = Author()\n>>> f = AuthorForm(request.POST, instance=a)\n\n# Create and save the new author instance. There's no need to do anything else.\n>>> new_author = f.save()\nOther than the save() and save_m2m() methods, a ModelForm works\nexactly the same way as any other forms form. For example, the\nis_valid() method is used to check for validity, the is_multipart()\nmethod is used to determine whether a form requires multipart file upload (and\nhence whether request.FILES must be passed to the form), etc. See\nBinding uploaded files to a form for more information.
It is strongly recommended that you explicitly set all fields that should be\nedited in the form using the fields attribute. Failure to do so can easily\nlead to security problems when a form unexpectedly allows a user to set certain\nfields, especially when new fields are added to a model. Depending on how the\nform is rendered, the problem may not even be visible on the web page.
The alternative approach would be to include all fields automatically, or\nremove only some. This fundamental approach is known to be much less secure and\nhas led to serious exploits on major websites (e.g. GitHub\n).
\nThere are, however, two shortcuts available for cases where you can guarantee\nthese security concerns do not apply to you:
\nSet the fields attribute to the special value '__all__' to indicate\nthat all fields in the model should be used. For example:
from django.forms import ModelForm\n\n\nclass AuthorForm(ModelForm):\n class Meta:\n model = Author\n fields = "__all__"\nSet the exclude attribute of the ModelForm’s inner Meta class to\na list of fields to be excluded from the form.
Por ejemplo:
\nclass PartialAuthorForm(ModelForm):\n class Meta:\n model = Author\n exclude = ["title"]\nSince the Author model has the 3 fields name, title and\nbirth_date, this will result in the fields name and birth_date\nbeing present on the form.
If either of these are used, the order the fields appear in the form will be\nthe order the fields are defined in the model, with ManyToManyField\ninstances appearing last.
In addition, Django applies the following rule: if you set editable=False\non the model field, any form created from the model via ModelForm will\nnot include that field.
The default field types, as described in the Field types table above, are\nsensible defaults. If you have a DateField in your model, chances are you’d\nwant that to be represented as a DateField in your form. But ModelForm\ngives you the flexibility of changing the form field for a given model.
To specify a custom widget for a field, use the widgets attribute of the\ninner Meta class. This should be a dictionary mapping field names to widget\nclasses or instances.
For example, if you want the CharField for the name attribute of\nAuthor to be represented by a <textarea> instead of its default\n<input type="text">, you can override the field’s widget:
from django.forms import ModelForm, Textarea\nfrom myapp.models import Author\n\n\nclass AuthorForm(ModelForm):\n class Meta:\n model = Author\n fields = ["name", "title", "birth_date"]\n widgets = {\n "name": Textarea(attrs={"cols": 80, "rows": 20}),\n }\nThe widgets dictionary accepts either widget instances (e.g.,\nTextarea(...)) or classes (e.g., Textarea). Note that the widgets\ndictionary is ignored for a model field with a non-empty choices attribute.\nIn this case, you must override the form field to use a different widget.
Similarly, you can specify the labels, help_texts and\nerror_messages attributes of the inner Meta class if you want to\nfurther customize a field.
For example if you wanted to customize the wording of all user facing strings\nfor the name field:
from django.utils.translation import gettext_lazy as _\n\n\nclass AuthorForm(ModelForm):\n class Meta:\n model = Author\n fields = ["name", "title", "birth_date"]\n labels = {\n "name": _("Writer"),\n }\n help_texts = {\n "name": _("Some useful help text."),\n }\n error_messages = {\n "name": {\n "max_length": _("This writer's name is too long."),\n },\n }\nYou can also specify field_classes or formfield_callback to customize\nthe type of fields instantiated by the form.
For example, if you wanted to use MySlugFormField for the slug\nfield, you could do the following:
from django.forms import ModelForm\nfrom myapp.models import Article\n\n\nclass ArticleForm(ModelForm):\n class Meta:\n model = Article\n fields = ["pub_date", "headline", "content", "reporter", "slug"]\n field_classes = {\n "slug": MySlugFormField,\n }\no:
\nfrom django.forms import ModelForm\nfrom myapp.models import Article\n\n\ndef formfield_for_dbfield(db_field, **kwargs):\n if db_field.name == "slug":\n return MySlugFormField()\n return db_field.formfield(**kwargs)\n\n\nclass ArticleForm(ModelForm):\n class Meta:\n model = Article\n fields = ["pub_date", "headline", "content", "reporter", "slug"]\n formfield_callback = formfield_for_dbfield\nFinally, if you want complete control over of a field – including its type,\nvalidators, required, etc. – you can do this by declaratively specifying\nfields like you would in a regular Form.
If you want to specify a field’s validators, you can do so by defining\nthe field declaratively and setting its validators parameter:
from django.forms import CharField, ModelForm\nfrom myapp.models import Article\n\n\nclass ArticleForm(ModelForm):\n slug = CharField(validators=[validate_slug])\n\n class Meta:\n model = Article\n fields = ["pub_date", "headline", "content", "reporter", "slug"]\nBy default, the fields in a ModelForm will not localize their data. To\nenable localization for fields, you can use the localized_fields\nattribute on the Meta class.
>>> from django.forms import ModelForm\n>>> from myapp.models import Author\n>>> class AuthorForm(ModelForm):\n... class Meta:\n... model = Author\n... localized_fields = ['birth_date']\nIf localized_fields is set to the special value '__all__', all fields\nwill be localized.
As with basic forms, you can extend and reuse ModelForm classes by\ninheriting them. This is useful if you need to declare extra fields or extra\nmethods on a parent class for use in a number of forms derived from models.\nFor example, using the previous ArticleForm class:
>>> class EnhancedArticleForm(ArticleForm):\n... def clean_pub_date(self): ...\n...\nThis creates a form that behaves identically to ArticleForm, except there’s\nsome extra validation and cleaning for the pub_date field.
You can also subclass the parent’s Meta inner class if you want to change\nthe Meta.fields or Meta.exclude lists:
>>> class RestrictedArticleForm(EnhancedArticleForm):\n... class Meta(ArticleForm.Meta):\n... exclude = ["body"]\n...\nThis adds the extra method from the EnhancedArticleForm and modifies\nthe original ArticleForm.Meta to remove one field.
There are a couple of things to note, however.
\nNormal Python name resolution rules apply. If you have multiple base\nclasses that declare a Meta inner class, only the first one will be\nused. This means the child’s Meta, if it exists, otherwise the\nMeta of the first parent, etc.
It’s possible to inherit from both Form and ModelForm simultaneously,\nhowever, you must ensure that ModelForm appears first in the MRO. This is\nbecause these classes rely on different metaclasses and a class can only have\none metaclass.
It’s possible to declaratively remove a Field inherited from a parent\nclass by setting the name to be None on the subclass.
You can only use this technique to opt out from a field defined declaratively\nby a parent class; it won’t prevent the ModelForm metaclass from\ngenerating a default field. To opt-out from default fields, see\nSelecting the fields to use.
As with regular forms, it’s possible to specify initial data for forms by\nspecifying an initial parameter when instantiating the form. Initial\nvalues provided this way will override both initial values from the form field\nand values from an attached model instance. For example:
>>> article = Article.objects.get(pk=1)\n>>> article.headline\n'My headline'\n>>> form = ArticleForm(initial={"headline": "Initial headline"}, instance=article)\n>>> form["headline"].value()\n'Initial headline'\nYou can create forms from a given model using the standalone function\nmodelform_factory(), instead of using a class\ndefinition. This may be more convenient if you do not have many customizations\nto make:
>>> from django.forms import modelform_factory\n>>> from myapp.models import Book\n>>> BookForm = modelform_factory(Book, fields=["author", "title"])\nThis can also be used to make modifications to existing forms, for example by\nspecifying the widgets to be used for a given field:
\n>>> from django.forms import Textarea\n>>> Form = modelform_factory(Book, form=BookForm, widgets={"title": Textarea()})\nThe fields to include can be specified using the fields and exclude\nkeyword arguments, or the corresponding attributes on the ModelForm inner\nMeta class. Please see the ModelForm Selecting the fields to use\ndocumentation.
… or enable localization for specific fields:
\n>>> Form = modelform_factory(Author, form=AuthorForm, localized_fields=["birth_date"])\nLike regular formsets, Django provides a couple\nof enhanced formset classes to make working with Django models more\nconvenient. Let’s reuse the Author model from above:
>>> from django.forms import modelformset_factory\n>>> from myapp.models import Author\n>>> AuthorFormSet = modelformset_factory(Author, fields=["name", "title"])\nUsing fields restricts the formset to use only the given fields.\nAlternatively, you can take an «opt-out» approach, specifying which fields to\nexclude:
>>> AuthorFormSet = modelformset_factory(Author, exclude=["birth_date"])\nThis will create a formset that is capable of working with the data associated\nwith the Author model. It works just like a regular formset:
>>> formset = AuthorFormSet()\n>>> print(formset)\n<input type="hidden" name="form-TOTAL_FORMS" value="1" id="id_form-TOTAL_FORMS"><input type="hidden" name="form-INITIAL_FORMS" value="0" id="id_form-INITIAL_FORMS"><input type="hidden" name="form-MIN_NUM_FORMS" value="0" id="id_form-MIN_NUM_FORMS"><input type="hidden" name="form-MAX_NUM_FORMS" value="1000" id="id_form-MAX_NUM_FORMS">\n<div><label for="id_form-0-name">Name:</label><input id="id_form-0-name" type="text" name="form-0-name" maxlength="100"></div>\n<div><label for="id_form-0-title">Title:</label><select name="form-0-title" id="id_form-0-title">\n<option value="" selected>---------</option>\n<option value="MR">Mr.</option>\n<option value="MRS">Mrs.</option>\n<option value="MS">Ms.</option>\n</select><input type="hidden" name="form-0-id" id="id_form-0-id"></div>\nBy default, when you create a formset from a model, the formset will use a\nqueryset that includes all objects in the model (e.g.,\nAuthor.objects.all()). You can override this behavior by using the\nqueryset argument:
>>> formset = AuthorFormSet(queryset=Author.objects.filter(name__startswith="O"))\nAlternatively, you can create a subclass that sets self.queryset in\n__init__:
from django.forms import BaseModelFormSet\nfrom myapp.models import Author\n\n\nclass BaseAuthorFormSet(BaseModelFormSet):\n def __init__(self, *args, **kwargs):\n super().__init__(*args, **kwargs)\n self.queryset = Author.objects.filter(name__startswith="O")\nThen, pass your BaseAuthorFormSet class to the factory function:
>>> AuthorFormSet = modelformset_factory(\n... Author, fields=["name", "title"], formset=BaseAuthorFormSet\n... )\nIf you want to return a formset that doesn’t include any preexisting\ninstances of the model, you can specify an empty QuerySet:
\n>>> AuthorFormSet(queryset=Author.objects.none())\nBy default, when you use modelformset_factory, a model form will\nbe created using modelform_factory().\nOften, it can be useful to specify a custom model form. For example,\nyou can create a custom model form that has custom validation:
class AuthorForm(forms.ModelForm):\n class Meta:\n model = Author\n fields = ["name", "title"]\n\n def clean_name(self):\n # custom validation for the name field\n ...\nThen, pass your model form to the factory function:
\nAuthorFormSet = modelformset_factory(Author, form=AuthorForm)\nIt is not always necessary to define a custom model form. The\nmodelformset_factory function has several arguments which are\npassed through to modelform_factory, which are described below.
widgetsLink to this heading#Using the widgets parameter, you can specify a dictionary of values to\ncustomize the ModelForm’s widget class for a particular field. This\nworks the same way as the widgets dictionary on the inner Meta\nclass of a ModelForm works:
>>> AuthorFormSet = modelformset_factory(\n... Author,\n... fields=["name", "title"],\n... widgets={"name": Textarea(attrs={"cols": 80, "rows": 20})},\n... )\nlocalized_fieldsLink to this heading#Using the localized_fields parameter, you can enable localization for\nfields in the form.
>>> AuthorFormSet = modelformset_factory(\n... Author, fields=['name', 'title', 'birth_date'],\n... localized_fields=['birth_date'])\nIf localized_fields is set to the special value '__all__', all fields\nwill be localized.
As with regular formsets, it’s possible to specify initial data for forms in the formset by specifying an initial\nparameter when instantiating the model formset class returned by\nmodelformset_factory(). However, with model\nformsets, the initial values only apply to extra forms, those that aren’t\nattached to an existing model instance. If the length of initial exceeds\nthe number of extra forms, the excess initial data is ignored. If the extra\nforms with initial data aren’t changed by the user, they won’t be validated or\nsaved.
As with a ModelForm, you can save the data as a model object. This is done\nwith the formset’s save() method:
# Create a formset instance with POST data.\n>>> formset = AuthorFormSet(request.POST)\n\n# Assuming all is valid, save the data.\n>>> instances = formset.save()\nThe save() method returns the instances that have been saved to the\ndatabase. If a given instance’s data didn’t change in the bound data, the\ninstance won’t be saved to the database and won’t be included in the return\nvalue (instances, in the above example).
When fields are missing from the form (for example because they have been\nexcluded), these fields will not be set by the save() method. You can find\nmore information about this restriction, which also holds for regular\nmodel forms, in Selecting the fields to use.
Pass commit=False to return the unsaved model instances:
# don't save to the database\n>>> instances = formset.save(commit=False)\n>>> for instance in instances:\n... # do something with instance\n... instance.save()\n...\nThis gives you the ability to attach data to the instances before saving them\nto the database. If your formset contains a ManyToManyField, you’ll also\nneed to call formset.save_m2m() to ensure the many-to-many relationships\nare saved properly.
After calling save(), your model formset will have three new attributes\ncontaining the formset’s changes:
As with regular formsets, you can use the max_num and extra parameters\nto modelformset_factory() to limit the number of\nextra forms displayed.
max_num does not prevent existing objects from being displayed:
>>> Author.objects.order_by("name")\n<QuerySet [<Author: Charles Baudelaire>, <Author: Paul Verlaine>, <Author: Walt Whitman>]>\n\n>>> AuthorFormSet = modelformset_factory(Author, fields=["name"], max_num=1)\n>>> formset = AuthorFormSet(queryset=Author.objects.order_by("name"))\n>>> [x.name for x in formset.get_queryset()]\n['Charles Baudelaire', 'Paul Verlaine', 'Walt Whitman']\nAlso, extra=0 doesn’t prevent creation of new model instances as you can\nadd additional forms with JavaScript\nor send additional POST data. See Preventing new objects creation on how to do\nthis.
If the value of max_num is greater than the number of existing related\nobjects, up to extra additional blank forms will be added to the formset,\nso long as the total number of forms does not exceed max_num:
>>> AuthorFormSet = modelformset_factory(Author, fields=["name"], max_num=4, extra=2)\n>>> formset = AuthorFormSet(queryset=Author.objects.order_by("name"))\n>>> for form in formset:\n... print(form)\n...\n<div><label for="id_form-0-name">Name:</label><input id="id_form-0-name" type="text" name="form-0-name" value="Charles Baudelaire" maxlength="100"><input type="hidden" name="form-0-id" value="1" id="id_form-0-id"></div>\n<div><label for="id_form-1-name">Name:</label><input id="id_form-1-name" type="text" name="form-1-name" value="Paul Verlaine" maxlength="100"><input type="hidden" name="form-1-id" value="3" id="id_form-1-id"></div>\n<div><label for="id_form-2-name">Name:</label><input id="id_form-2-name" type="text" name="form-2-name" value="Walt Whitman" maxlength="100"><input type="hidden" name="form-2-id" value="2" id="id_form-2-id"></div>\n<div><label for="id_form-3-name">Name:</label><input id="id_form-3-name" type="text" name="form-3-name" maxlength="100"><input type="hidden" name="form-3-id" id="id_form-3-id"></div>\nA max_num value of None (the default) puts a high limit on the number\nof forms displayed (1000). In practice this is equivalent to no limit.
Using the edit_only parameter, you can prevent creation of any new\nobjects:
>>> AuthorFormSet = modelformset_factory(\n... Author,\n... fields=["name", "title"],\n... edit_only=True,\n... )\nHere, the formset will only edit existing Author instances. No other\nobjects will be created or edited.
Model formsets are very similar to formsets. Let’s say we want to present a\nformset to edit Author model instances:
from django.forms import modelformset_factory\nfrom django.shortcuts import render\nfrom myapp.models import Author\n\n\ndef manage_authors(request):\n AuthorFormSet = modelformset_factory(Author, fields=["name", "title"])\n if request.method == "POST":\n formset = AuthorFormSet(request.POST, request.FILES)\n if formset.is_valid():\n formset.save()\n # do something.\n else:\n formset = AuthorFormSet()\n return render(request, "manage_authors.html", {"formset": formset})\nAs you can see, the view logic of a model formset isn’t drastically different\nthan that of a «normal» formset. The only difference is that we call\nformset.save() to save the data into the database. (This was described\nabove, in Saving objects in the formset.)
clean() on a ModelFormSetLink to this heading#Just like with a ModelForm, by default the clean() method of a\nModelFormSet will validate that none of the items in the formset violate\nthe unique constraints on your model (either unique, unique_together or\nunique_for_date|month|year). If you want to override the clean() method\non a ModelFormSet and maintain this validation, you must call the parent\nclass’s clean method:
from django.forms import BaseModelFormSet\n\n\nclass MyModelFormSet(BaseModelFormSet):\n def clean(self):\n super().clean()\n # example custom validation across forms in the formset\n for form in self.forms:\n # your custom formset validation\n ...\nAlso note that by the time you reach this step, individual model instances\nhave already been created for each Form. Modifying a value in\nform.cleaned_data is not sufficient to affect the saved value. If you wish\nto modify a value in ModelFormSet.clean() you must modify\nform.instance:
from django.forms import BaseModelFormSet\n\n\nclass MyModelFormSet(BaseModelFormSet):\n def clean(self):\n super().clean()\n\n for form in self.forms:\n name = form.cleaned_data["name"].upper()\n form.cleaned_data["name"] = name\n # update the instance value.\n form.instance.name = name\nAs stated earlier, you can override the default queryset used by the model\nformset:
\nfrom django.forms import modelformset_factory\nfrom django.shortcuts import render\nfrom myapp.models import Author\n\n\ndef manage_authors(request):\n AuthorFormSet = modelformset_factory(Author, fields=["name", "title"])\n queryset = Author.objects.filter(name__startswith="O")\n if request.method == "POST":\n formset = AuthorFormSet(\n request.POST,\n request.FILES,\n queryset=queryset,\n )\n if formset.is_valid():\n formset.save()\n # Do something.\n else:\n formset = AuthorFormSet(queryset=queryset)\n return render(request, "manage_authors.html", {"formset": formset})\nNote that we pass the queryset argument in both the POST and GET\ncases in this example.
There are three ways to render a formset in a Django template.
\nFirst, you can let the formset do most of the work:
\n<form method="post">\n {{ formset }}\n</form>\nSecond, you can manually render the formset, but let the form deal with\nitself:
\n<form method="post">\n {{ formset.management_form }}\n {% for form in formset %}\n {{ form }}\n {% endfor %}\n</form>\nWhen you manually render the forms yourself, be sure to render the management\nform as shown above. See the management form documentation.
\nThird, you can manually render each field:
\n<form method="post">\n {{ formset.management_form }}\n {% for form in formset %}\n {% for field in form %}\n {{ field.label_tag }} {{ field }}\n {% endfor %}\n {% endfor %}\n</form>\nIf you opt to use this third method and you don’t iterate over the fields with\na {% for %} loop, you’ll need to render the primary key field. For example,\nif you were rendering the name and age fields of a model:
<form method="post">\n {{ formset.management_form }}\n {% for form in formset %}\n {{ form.id }}\n <ul>\n <li>{{ form.name }}</li>\n <li>{{ form.age }}</li>\n </ul>\n {% endfor %}\n</form>\nNotice how we need to explicitly render {{ form.id }}. This ensures that\nthe model formset, in the POST case, will work correctly. (This example\nassumes a primary key named id. If you’ve explicitly defined your own\nprimary key that isn’t called id, make sure it gets rendered.)
Inline formsets is a small abstraction layer on top of model formsets. These\nsimplify the case of working with related objects via a foreign key. Suppose\nyou have these two models:
\nfrom django.db import models\n\n\nclass Author(models.Model):\n name = models.CharField(max_length=100)\n\n\nclass Book(models.Model):\n author = models.ForeignKey(Author, on_delete=models.CASCADE)\n title = models.CharField(max_length=100)\nIf you want to create a formset that allows you to edit books belonging to\na particular author, you could do this:
\n>>> from django.forms import inlineformset_factory\n>>> BookFormSet = inlineformset_factory(Author, Book, fields=["title"])\n>>> author = Author.objects.get(name="Mike Royko")\n>>> formset = BookFormSet(instance=author)\nBookFormSet’s prefix is 'book_set'\n(<model name>_set ). If Book’s ForeignKey to Author has a\nrelated_name, that’s used instead.
InlineFormSetLink to this heading#When overriding methods on InlineFormSet, you should subclass\nBaseInlineFormSet rather than\nBaseModelFormSet.
For example, if you want to override clean():
from django.forms import BaseInlineFormSet\n\n\nclass CustomInlineFormSet(BaseInlineFormSet):\n def clean(self):\n super().clean()\n # example custom validation across forms in the formset\n for form in self.forms:\n # your custom formset validation\n ...\nSee also Overriding clean() on a ModelFormSet.
\nThen when you create your inline formset, pass in the optional argument\nformset:
>>> from django.forms import inlineformset_factory\n>>> BookFormSet = inlineformset_factory(\n... Author, Book, fields=["title"], formset=CustomInlineFormSet\n... )\n>>> author = Author.objects.get(name="Mike Royko")\n>>> formset = BookFormSet(instance=author)\nIf your model contains more than one foreign key to the same model, you’ll\nneed to resolve the ambiguity manually using fk_name. For example, consider\nthe following model:
class Friendship(models.Model):\n from_friend = models.ForeignKey(\n Friend,\n on_delete=models.CASCADE,\n related_name="from_friends",\n )\n to_friend = models.ForeignKey(\n Friend,\n on_delete=models.CASCADE,\n related_name="friends",\n )\n length_in_months = models.IntegerField()\nTo resolve this, you can use fk_name to\ninlineformset_factory():
>>> FriendshipFormSet = inlineformset_factory(\n... Friend, Friendship, fk_name="from_friend", fields=["to_friend", "length_in_months"]\n... )\nYou may want to provide a view that allows a user to edit the related objects\nof a model. Here’s how you can do that:
\ndef manage_books(request, author_id):\n author = Author.objects.get(pk=author_id)\n BookInlineFormSet = inlineformset_factory(Author, Book, fields=["title"])\n if request.method == "POST":\n formset = BookInlineFormSet(request.POST, request.FILES, instance=author)\n if formset.is_valid():\n formset.save()\n # Do something. Should generally end with a redirect. For example:\n return HttpResponseRedirect(author.get_absolute_url())\n else:\n formset = BookInlineFormSet(instance=author)\n return render(request, "manage_books.html", {"formset": formset})\nNotice how we pass instance in both the POST and GET cases.
inlineformset_factory uses modelformset_factory and passes most\nof its arguments to modelformset_factory. This means you can use\nthe widgets parameter in much the same way as passing it to\nmodelformset_factory. See Specifying widgets to use in the form with\nwidgets above.