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uuid model field

Author:
newspire
Posted:
December 23, 2008
Language:
Python
Version:
1.0
Tags:
model field uuid universally-unique-identifier
Score:
2 (after 2 ratings)

This code provides a primary key field that is globally unique. It uses the pre_save method to auto-populate the field with a Universal Unique Id as the record is saved the first time.

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from django.db import models
import uuid


class UUIDField(models.CharField) :
    
    def __init__(self, *args, **kwargs):
        kwargs['max_length'] = kwargs.get('max_length', 64 )
        kwargs['blank'] = True
        models.CharField.__init__(self, *args, **kwargs)
    
    def pre_save(self, model_instance, add):
        if add :
            value = str(uuid.uuid4())
            setattr(model_instance, self.attname, value)
            return value
        else:
            return super(models.CharField, self).pre_save(model_instance, add)


class Example(models.Model) :
    uuid = UUIDField(primary_key=True, editable=False)
    name = models.CharField(max_length=32)
    value = models.CharField(max_length=255, blank=True)

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Comments

manfre (on August 10, 2009):
<p>It seems like it would be better to simply pass a default to a CharField? At least then the uuid will be assigned before the object is saved, which is useful when dealing with a Model that stores files.</p> <p>from uuid import uuid4 uuid = models.CharField(primary_key=True, max_length=64, editable=False, blank=True, default=uuid4)</p>

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tgandor (on June 24, 2014):
<p>@manfre:</p> <p>well, I was also pursuing your simpler solution (default = uuid.uuid4) and stuff, but I got some problems when trying to migrate my initial South migration:</p> <p>ValueError: Cannot successfully create field 'hash' for model 'token': name 'UUID' is not defined.</p> <p>I will look into it, but I'm afraid there will have to be some in-model hacking like the one above...</p> <p>Right now, my code is as simple as could be:</p> <pre>from django.db import models from uuid import uuid4 class Token(models.Model): hash = models.CharField(max_length=250, unique=True, null=False, blank=False, default=uuid4) def __unicode__(self): return hash </pre>

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arunkreddy (on February 5, 2015):
<p>max_length attribute could be set to 32 after replacing the '-' with '' in the string returned by uuid4.</p>

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