Get model's fields in Django

Given a Django model, I'm trying to list all of its fields. I've seen some examples of doing this using the _meta model attribute, but doesn't the underscore in front of meta indicate that the _meta attribute is a private attribute and shouldn't be accessed directly? ... Because, for example, the layout of _meta could change in the future and not be a stable API?

Is _meta an exception to this rule? Is it stable and ready to use or is it considered bad practice to access it? Or is there a function or some other way to introspect the fields of a model without using the _meta attribute? Below is a list of some links showing how to do this using the _meta attribute

Any advice is much appreciated.

django object get/set field

http://www.djangofoo.com/80/get-list-model-fields

How to introspect django model fields?

Solution 1:

_meta is private, but it's relatively stable. There are efforts to formalise it, document it and remove the underscore, which might happen before 1.3 or 1.4. I imagine effort will be made to ensure things are backwards compatible, because lots of people have been using it anyway.

If you're particularly concerned about compatibility, write a function that takes a model and returns the fields. This means if something does change in the future, you only have to change one function.

def get_model_fields(model):
    return model._meta.fields

I believe this will return a list of Field objects. To get the value of each field from the instance, use getattr(instance, field.name).

Update: Django contributors are working on an API to replace the _Meta object as part of a Google Summer of Code. See:
- https://groups.google.com/forum/#!topic/django-developers/hD4roZq0wyk
- https://code.djangoproject.com/wiki/new_meta_api

Solution 2:

I know this post is pretty old, but I just cared to tell anyone who is searching for the same thing that there is a public and official API to do this: get_fields() and get_field()

Usage:

fields = model._meta.get_fields()
my_field = model._meta.get_field('my_field')

https://docs.djangoproject.com/en/3.2/ref/models/meta/#retrieving-all-field-instances-of-a-model

Solution 3:

get_fields() returns a tuple and each element is a Model field type, which can't be used directly as a string. So, field.name will return the field name

my_model_fields = [field.name for field in MyModel._meta.get_fields()]
The above code will return a list conatining all fields name

Example

In [11]: from django.contrib.auth.models import User

In [12]: User._meta.get_fields()
Out[12]: 
(<ManyToOneRel: admin.logentry>,
 <django.db.models.fields.AutoField: id>,
 <django.db.models.fields.CharField: password>,
 <django.db.models.fields.DateTimeField: last_login>,
 <django.db.models.fields.BooleanField: is_superuser>,
 <django.db.models.fields.CharField: username>,
 <django.db.models.fields.CharField: first_name>,
 <django.db.models.fields.CharField: last_name>,
 <django.db.models.fields.EmailField: email>,
 <django.db.models.fields.BooleanField: is_staff>,
 <django.db.models.fields.BooleanField: is_active>,
 <django.db.models.fields.DateTimeField: date_joined>,
 <django.db.models.fields.related.ManyToManyField: groups>,
 <django.db.models.fields.related.ManyToManyField: user_permissions>)

In [13]: [field.name for field in User._meta.get_fields()]
Out[13]: 
['logentry',
 'id',
 'password',
 'last_login',
 'is_superuser',
 'username',
 'first_name',
 'last_name',
 'email',
 'is_staff',
 'is_active',
 'date_joined',
 'groups',
 'user_permissions']

Solution 4:

Now there is special method - get_fields()

    >>> from django.contrib.auth.models import User
    >>> User._meta.get_fields()

It accepts two parameters that can be used to control which fields are returned:

• include_parents

  True by default. Recursively includes fields defined on parent classes. If set to False, get_fields() will only search for fields declared directly on the current model. Fields from models that directly inherit from abstract models or proxy classes are considered to be local, not on the parent.

• include_hidden

  False by default. If set to True, get_fields() will include fields that are used to back other field’s functionality. This will also include any fields that have a related_name (such as ManyToManyField, or ForeignKey) that start with a “+”

Solution 5:

This is something that is done by Django itself when building a form from a model. It is using the _meta attribute, but as Bernhard noted, it uses both _meta.fields and _meta.many_to_many. Looking at django.forms.models.fields_for_model, this is how you could do it:

opts = model._meta
for f in sorted(opts.fields + opts.many_to_many):
    print '%s: %s' % (f.name, f)