How do I create a slug in Django?

Question

I am trying to create a SlugField in Django.

I created this simple model:

from django.db import models

class Test(models.Model):
    q = models.CharField(max_length=30)
    s = models.SlugField()

I then do this:

>>> from mysite.books.models import Test
>>> t=Test(q="aa a a a", s="b b b b")
>>> t.s
'b b b b'
>>> t.save()
>>> t.s
'b b b b'

I was expecting b-b-b-b.

Answer 1

You will need to use the slugify function.

>>> from django.template.defaultfilters import slugify
>>> slugify("b b b b")
u'b-b-b-b'
>>>

You can call slugify automatically by overriding the save method:

class Test(models.Model):
    q = models.CharField(max_length=30)
    s = models.SlugField()
    
    def save(self, *args, **kwargs):
        self.s = slugify(self.q)
        super(Test, self).save(*args, **kwargs)

Be aware that the above will cause your URL to change when the q field is edited, which can cause broken links. It may be preferable to generate the slug only once when you create a new object:

class Test(models.Model):
    q = models.CharField(max_length=30)
    s = models.SlugField()
    
    def save(self, *args, **kwargs):
        if not self.id:
            # Newly created object, so set slug
            self.s = slugify(self.q)

        super(Test, self).save(*args, **kwargs)

Answer 2

There is corner case with some utf-8 characters

Example:

>>> from django.template.defaultfilters import slugify
>>> slugify(u"test ąęśćółń")
u'test-aescon' # there is no "l"

This can be solved with Unidecode

>>> from unidecode import unidecode
>>> from django.template.defaultfilters import slugify
>>> slugify(unidecode(u"test ąęśćółń"))
u'test-aescoln'

Answer 3

A small correction to Thepeer's answer: To override save() function in model classes, better add arguments to it:

from django.utils.text import slugify

def save(self, *args, **kwargs):
    if not self.id:
        self.s = slugify(self.q)

    super(test, self).save(*args, **kwargs)

Otherwise, test.objects.create(q="blah blah blah") will result in a force_insert error (unexpected argument).

Answer 4

If you're using the admin interface to add new items of your model, you can set up a ModelAdmin in your admin.py and utilize prepopulated_fields to automate entering of a slug:

class ClientAdmin(admin.ModelAdmin):
    prepopulated_fields = {'slug': ('name',)}

admin.site.register(Client, ClientAdmin)

Here, when the user enters a value in the admin form for the name field, the slug will be automatically populated with the correct slugified name.

Answer 5

In most cases the slug should not change, so you really only want to calculate it on first save:

class Test(models.Model):
    q = models.CharField(max_length=30)
    s = models.SlugField(editable=False) # hide from admin

    def save(self):
        if not self.id:
            self.s = slugify(self.q)

        super(Test, self).save()

Answer 6

If you don't want to set the slugfield to Not be editable, then I believe you'll want to set the Null and Blank properties to False. Otherwise you'll get an error when trying to save in Admin.

So a modification to the above example would be::

class test(models.Model):
    q = models.CharField(max_length=30)
    s = models.SlugField(null=True, blank=True) # Allow blank submission in admin.

    def save(self):
        if not self.id:
            self.s = slugify(self.q)

        super(test, self).save()

Answer 7

Use prepopulated_fields in your admin class:

class ArticleAdmin(admin.ModelAdmin):
    prepopulated_fields = {"slug": ("title",)}

admin.site.register(Article, ArticleAdmin)

Answer 8

I'm using Django 1.7

Create a SlugField in your model like this:

slug = models.SlugField()

Then in admin.py define prepopulated_fields;

class ArticleAdmin(admin.ModelAdmin):
    prepopulated_fields = {"slug": ("title",)}

Answer 9

You can look at the docs for the SlugField to get to know more about it in more descriptive way.

Answer 10

You can create slug field with SlugField() and slugify a name field value with slugify(), then save the slugified name field value as a slug field value in overridden save() every time you add and change a Product object as shown below:

# "models.py"

from django.utils.text import slugify

class Product(models.Model):
    name = models.CharField(max_length=20)
    slug = models.SlugField()
    
    def save(self, *args, **kwargs):
        self.slug = slugify(self.name)
        super().save(*args, **kwargs)

And, you can prevent broken links by using id in addition to slug in the url as shown below:

                         # ↓ "slug" ↓
http://myshop.com/product/orange-juice/id
                                 # "id" ↑

So, the url takes id in addition to slug in urls.py as shown below:

# "urls.py"

urlpatterns = [
    path(      # ↓ "slug" ↓　
        'product/<slug:slug>/<int:id>/', 
        views.get_product, # ↑ "id" ↑
        name="get_product"
    )
]

Then, you should treat only id not treating slug in get_product() in views.py as shown below:

# "views.py"

def get_product(request, id=None, slug=None):
    product_obj = None

    if id:
        product_obj = Product.objects.get(id=id)
    
    return HttpResponse(product_obj)

Answer 11

In some cases slugify isn't enough standalone. I'm using a different technique for slugs. I think this will cover most scenarios.

First create a slug.py file in your app directory and copy the following codes in it.

slug.py

import re
from django.template.defaultfilters import slugify


def unique_slugify(instance, value, slug_field_name='slug', queryset=None,
                   slug_separator='-'):
    """
    Calculates and stores a unique slug of ``value`` for an instance.
    ``slug_field_name`` should be a string matching the name of the field to
    store the slug in (and the field to check against for uniqueness).
    ``queryset`` usually doesn't need to be explicitly provided - it'll default
    to using the ``.all()`` queryset from the model's default manager.
    """
    slug_field = instance._meta.get_field(slug_field_name)

    slug = getattr(instance, slug_field.attname)
    slug_len = slug_field.max_length

    # Sort out the initial slug, limiting its length if necessary.
    slug = slugify(value)
    if slug_len:
        slug = slug[:slug_len]
    slug = _slug_strip(slug, slug_separator)
    original_slug = slug

    # Create the queryset if one wasn't explicitly provided and exclude the
    # current instance from the queryset.
    if queryset is None:
        queryset = instance.__class__._default_manager.all()
    if instance.pk:
        queryset = queryset.exclude(pk=instance.pk)

    # Find a unique slug. If one matches, at '-2' to the end and try again
    # (then '-3', etc).
    next = 2
    while not slug or queryset.filter(**{slug_field_name: slug}):
        slug = original_slug
        end = '%s%s' % (slug_separator, next)
        if slug_len and len(slug) + len(end) > slug_len:
            slug = slug[:slug_len-len(end)]
            slug = _slug_strip(slug, slug_separator)
        slug = '%s%s' % (slug, end)
        next += 1

    setattr(instance, slug_field.attname, slug)


def _slug_strip(value, separator='-'):
    """
    Cleans up a slug by removing slug separator characters that occur at the
    beginning or end of a slug.
    If an alternate separator is used, it will also replace any instances of
    the default '-' separator with the new separator.
    """
    separator = separator or ''
    if separator == '-' or not separator:
        re_sep = '-'
    else:
        re_sep = '(?:-|%s)' % re.escape(separator)
    # Remove multiple instances and if an alternate separator is provided,
    # replace the default '-' separator.
    if separator != re_sep:
        value = re.sub('%s+' % re_sep, separator, value)
    # Remove separator from the beginning and end of the slug.
    if separator:
        if separator != '-':
            re_sep = re.escape(separator)
        value = re.sub(r'^%s+|%s+$' % (re_sep, re_sep), '', value)
    return value

Then in your models.py import unique_slugify from that file. Then use it in save() method.

models.py

from django.db import models
from yourapp.slug import unique_slugify # Change "yourapp" with your app name

class Test(models.Model):
    q = models.CharField(max_length=30)
    s = models.SlugField()

    def save(self, **kwargs):
        slug = '%s' % (self.q)
        unique_slugify(self, slug)
        super(Test, self).save()