auto_now using signals

# Takes model and fieldname and sets field to current datetime on pre_save
def auto_now_on_save(model, fieldname):
	from django.db.models import signals
	from django.dispatch import dispatcher
	def _update_datefield(instance):
		from datetime import datetime
		setattr(instance, fieldname,
	dispatcher.connect(_update_datefield, signal=signals.pre_save, sender=model, weak=False)

More like this

  1. Analogue template filter to removetags that also removes the content of the tag by piquadrat 3 years, 5 months ago
  2. Skip only specified spaces by axil 2 years, 2 months ago
  3. Get stories by category and some date range by donnie demuth 5 years, 6 months ago
  4. Newforms Validation of Credit Card Numbers by humphreymurray 5 years, 11 months ago
  5. Smart Spaceless by btaylordesign 3 years ago


ericflo (on July 10, 2008):

It's good to know that for now that Django's signals are a fairly large performance hit. To remedy this, you can simply do this:

def save(self):
    self.myfield =
    super(MyModel, self).save()

It's one more line than if you import your solution and apply it to a field, but doesn't incur the performance penalty that signals currently entail.


(Forgotten your password?)