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unique_slugify

Author:
crucialfelix
Posted:
February 12, 2009
Language:
Python
Version:
1.0
Tags:
slug slugify
Score:
2 (after 2 ratings)

sorry, this is a duplicate post, original is here:

http://www.djangosnippets.org/snippets/690/

no way to delete snippets

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import re

from django.template.defaultfilters import slugify


def unique_slugify(instance, value, slug_field_name='slug', queryset=None,
                   slug_separator='-'):
    """
    Calculates 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)
    
    current_slug = getattr(instance, slug_field.attname)
    slug_len = slug_field.max_length

    # Sort out the initial slug. Chop its length down if we need to.
    slug = slugify(value)
    if slug_len:
        slug = slug[:slug_len]
    slug = _slug_strip(slug, slug_separator)
    original_slug = slug

    # Create a queryset, excluding the current instance.
    if not queryset:
        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' % 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)
    return slug

def _slug_strip(value, separator=None):
    """
    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.
    """
    if separator == '-' or not separator:
        re_sep = '-'
    else:
        re_sep = '(?:-|%s)' % re.escape(separator)
        value = re.sub('%s+' % re_sep, separator, value)
    return re.sub(r'^%s+|%s+$' % (re_sep, re_sep), '', value)

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Comments

seanos (on March 28, 2009):

Thanks for this.

One bug I found:

line 29 should be changed to:

if queryset is None:

otherwise if the argument queryset is empty, it will be re-populated with all rows from the model, leading to slug being modified when it should of been left alone.

#

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