def user_directory_path(instance, filename): 
# file will be uploaded to MEDIA_ROOT/user_<id>/<filename> 
return 'user_{0}/{1}'.format(instance.user.id, filename) 

class MyModel(models.Model): 
upload = models.FileField(upload_to=user_directory_path) 

import hashlib 
import os 
import time 
 
from django.utils.deconstruct import deconstructible 
 
 
@deconstructible
class TimeStampFileName(object): 
  def __init__(self, path): 
    self.path = os.path.join(path, "%s%s") 
 
  def __call__(self, instance, filename): 
    extension = os.path.splitext(filename)[1] 
    data = "%s_%d"%(filename,int(time.time())) 
    file_hash = hashlib.sha1(data).hexdigest() 
    return self.path % (file_hash, extension)

class MyModel(models.Model): 
  upload = models.FileField(upload_to=TimeStampFileName('media/'), )