Mypy stubs for Django
pep484 stubs for Django
This package contains type stubs and a custom mypy plugin to provide more precise static types and type inference for Django framework. Django uses some Python "magic" that makes having precise types for some code patterns problematic. This is why we need this project. The final goal is to be able to get precise types for most common patterns.
pip install django-stubs[compatible-mypy]
To make mypy aware of the plugin, you need to add
[mypy] plugins = mypy_django_plugin.main [mypy.plugins.django-stubs] django_settings_module = "myproject.settings"
pyproject.toml configurations are also supported:
[tool.mypy] plugins = ["mypy_django_plugin.main"] [tool.django-stubs] django_settings_module = "myproject.settings"
Two things happening here:
- We need to explicitly list our plugin to be loaded by
- Our plugin also requires
djangosettings module (what you put into
DJANGO_SETTINGS_MODULEvariable) to be specified
This fully working typed boilerplate can serve you as an example.
We rely on different
|django-stubs||Mypy version||Django version||Django partial support||Python version|
|4.2.0||1.2.x||4.2||4.1, 4.0, 3.2||3.7 - 3.11|
|1.16.0||1.1.x||4.1||4.0, 3.2||3.7 - 3.11|
|1.15.0||1.0.x||4.1||4.0, 3.2||3.7 - 3.11|
|1.14.0||0.990+||4.1||4.0, 3.2||3.7 - 3.11|
Type checking of Model Meta attributes
By inheriting from the
TypedModelMeta class, you can ensure you're using correct types for
from django.db import models from django_stubs_ext.db.models import TypedModelMeta class MyModel(models.Model): example = models.CharField(max_length=100) class Meta(TypedModelMeta): ordering = ["example"] constraints = [ models.UniqueConstraint(fields=["example"], name="unique_example"), ]
Is this an official Django project?
No, it is not. We are independent from Django at the moment. There's a proposal to merge our project into the Django itself. You can show your support by liking the PR.
Is it safe to use this in production?
Yes, it is! This project does not affect your runtime at all.
It only affects
mypy type checking process.
But, it does not make any sense to use this project without
mypy crashes when I run it with this plugin installed
The current implementation uses Django's runtime to extract information about models, so it might crash if your installed apps or
models.py are broken.
In other words, if your
manage.py runserver crashes, mypy will crash too.
You can also run
option to get extra information about the error.
I cannot use QuerySet or Manager with type annotations
You can get a
TypeError: 'type' object is not subscriptable
when you will try to use
Manager[MyModel] or some other Django-based Generic types.
This happens because these Django classes do not support
__class_getitem__ magic method in runtime.
You can go with our
django_stubs_exthelper, that patches all the types we use as Generic in django.
pip install django-stubs-ext # as a production dependency
And then place in your top-level settings:
import django_stubs_ext django_stubs_ext.monkeypatch()
Note: This monkey patching approach will only work when using Python 3.7 and higher, when the
__class_getitem__magic method was introduced.
You can add extra types to patch with
You can use strings instead:
'Manager[MyModel]', this way it will work as a type for
mypyand as a regular
How can I create a HttpRequest that's guaranteed to have an authenticated user?
Django's built in
HttpRequest has the attribute
user that resolves to the type
User is the user model specified by the
If you want a
HttpRequest that you can type-annotate with where you know that the user is authenticated you can subclass the normal
HttpRequest class like so:
from django.http import HttpRequest from my_user_app.models import MyUser class AuthenticatedHttpRequest(HttpRequest): user: MyUser
And then use
AuthenticatedHttpRequest instead of the standard
HttpRequest for when you know that the user is authenticated. For example in views using the
My QuerySet methods are returning Any rather than my Model
If you are using
from django.db import models class MyModelQuerySet(models.QuerySet): pass class MyModel(models.Model): bar = models.IntegerField() objects = MyModelQuerySet.as_manager() def use_my_model() -> int: foo = MyModel.objects.get(id=1) # Should now be `MyModel` return foo.xyz # Gives an error
Or if you're using
from django.db import models class MyModelQuerySet(models.QuerySet): pass MyModelManager = models.Manager.from_queryset(MyModelQuerySet) class MyModel(models.Model): bar = models.IntegerField() objects = MyModelManager() def use_my_model() -> int: foo = MyModel.objects.get(id=1) # Should now be `MyModel` return foo.xyz # Gives an error
Why am I getting incompatible return type errors on my custom managers?
If you declare your custom managers without generics and override built-in methods you might see an error message about incompatible error messages, something like this:
from django.db import models class MyManager(model.Manager): def create(self, **kwargs) -> "MyModel": pass
will cause this error message:
error: Return type "MyModel" of "create" incompatible with return type "_T" in supertype "BaseManager"
This is happening because the
Manager class is generic, but without
specifying generics the built-in manager methods are expected to return the
generic type of the base manager, which is any model. To fix this issue you
should declare your manager with your model as the type variable:
class MyManager(models.Manager["MyModel"]): ...
How do I annotate cases where I called QuerySet.annotate?
Django-stubs provides a special type,
django_stubs_ext.WithAnnotations[Model], which indicates that the
been annotated, meaning it allows getting/setting extra attributes on the model instance.
Optionally, you can provide a
TypedDict of these attributes,
WithAnnotations[MyModel, MyTypedDict], to specify which annotated attributes are present.
Currently, the mypy plugin can recognize that specific names were passed to
include them in the type, but does not record the types of these attributes.
The knowledge of the specific annotated fields is not yet used in creating more specific types for
filter methods, however knowledge that the model was annotated is used to create a
broader type result type for
values_list, and to allow
filtering on any field.
from typing import TypedDict from django_stubs_ext import WithAnnotations from django.db import models from django.db.models.expressions import Value class MyModel(models.Model): username = models.CharField(max_length=100) def func(m: WithAnnotations[MyModel]) -> str: return m.asdf # OK, since the model is annotated as allowing any attribute func(MyModel.objects.annotate(foo=Value("")).get(id=1)) # OK func( MyModel.objects.get(id=1) ) # Error, since this model will not allow access to any attribute class MyTypedDict(TypedDict): foo: str def func2(m: WithAnnotations[MyModel, MyTypedDict]) -> str: print(m.bar) # Error, since field "bar" is not in MyModel or MyTypedDict. return m.foo # OK, since we said field "foo" was allowed func(MyModel.objects.annotate(foo=Value("")).get(id=1)) # OK func(MyModel.objects.annotate(bar=Value("")).get(id=1)) # Error
How do I check if something is an instance of QuerySet in runtime?
A limitation of making
QuerySet generic is that you can not use
from django.db.models.query import QuerySet def foo(obj: object) -> None: if isinstance(obj, QuerySet): # Error: Parameterized generics cannot be used with class or instance checks ...
To get around with this issue without making
django_stubs_ext.QuerySetAny, a non-generic
QuerySet suitable for runtime type checking:
from django_stubs_ext import QuerySetAny def foo(obj: object) -> None: if isinstance(obj, QuerySetAny): # OK ...
Why am I getting incompatible argument type mentioning
The lazy translation functions of Django (such as
gettext_lazy) return a
Promise instead of
str. These two types cannot be used interchangeably. The return type of these functions was therefore changed to reflect that.
If you encounter this error in your own code, you can either cast the
str (causing the translation to be evaluated), or use the
StrOrPromise types from
django-stubs-ext in type hints. Which solution to choose depends depends on the particular case. See working with lazy translation objects in the Django documentation for more information.
If this is reported on Django code, please report an issue or open a pull request to fix the type hints.
awesome-python-typing- Awesome list of all typing-related things in Python.
djangorestframework-stubs- Stubs for Django REST Framework.
pytestplugin that we use for testing
mypystubs and plugins.
wemake-django-template- Create new typed Django projects in seconds.
To get help
We have Gitter here: https://gitter.im/mypy-django/Lobby If you think you have more generic typing issue, please refer to https://github.com/python/mypy and their Gitter.
This project is open source and community driven. As such we encourage contributions big and small. You can contribute by doing any of the following:
- Contribute code (e.g. improve stubs, add plugin capabilities, write tests etc) - to do so please follow the contribution guide.
- Assist in code reviews and discussions in issues.
- Identify bugs and issues and report these
- Ask and answer questions on StackOverflow
You can always also reach out in gitter to discuss your contributions!
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