gistfile1.py

from django.db import models
import os
import uuid


class MyModel(models.Model):

     
    def generate_new_filename(instance, filename):
        f, ext = os.path.splitext(filename)
        return '%s%s' % (uuid.uuid4().hex, ext)


    title = models.CharField(max_length=100)
    picture = models.ImageField(upload_to=generate_new_filename)

    def __unicode__(self):
        return self.title