django-signals

Identify the changed fields in django post_save signal Question: I’m using django’s post_save signal to execute some statements after saving the model. class Mode(models.Model): name = models.CharField(max_length=5) mode = models.BooleanField() from django.db.models.signals import post_save from django.dispatch import receiver @receiver(post_save, sender=Mode) def post_save(sender, instance, created, **kwargs): # do some stuff pass Now I want to execute …

Can I manually trigger signals in Django? Question: I’ve written some signals in my Django app that are supposed to send out an email when a particular model instance is created or modified, but the signal receiver function doesn’t seem to be responding; at any rate, I’m not getting any emails through (although I have …

django – comparing old and new field value before saving Question: I have a django model, and I need to compare old and new values of field BEFORE saving. I’ve tried the save() inheritance, and pre_save signal. It was triggered correctly, but I can’t find the list of actually changed fields and can’t compare old …

TransactionManagementError "You can't execute queries until the end of the 'atomic' block" while using signals, but only during Unit Testing Question: I am getting TransactionManagementError when trying to save a Django User model instance and in its post_save signal, I’m saving some models that have the user as the foreign key. The context and error …

when to use pre_save, save, post_save in django? Question: I see I can override or define pre_save, save, post_save to do what I want when a model instance gets saved. Which one is preferred in which situation and why? Asked By: eugene || Source Answers: pre_save it’s used before the transaction saves. post_save it’s used …

How do I mock a django signal handler? Question: I have a signal_handler connected through a decorator, something like this very simple one: @receiver(post_save, sender=User, dispatch_uid=’myfile.signal_handler_post_save_user’) def signal_handler_post_save_user(sender, *args, **kwargs): # do stuff What I want to do is to mock it with the mock library http://www.voidspace.org.uk/python/mock/ in a test, to check how many times …

Django post_save() signal implementation Question: I have a question about django. I have ManyToMany Models here class Product(models.Model): name = models.CharField(max_length=255) price = models.DecimalField(default=0.0, max_digits=9, decimal_places=2) stock = models.IntegerField(default=0) def __unicode__(self): return self.name class Cart(models.Model): customer = models.ForeignKey(Customer) products = models.ManyToManyField(Product, through=’TransactionDetail’) t_date = models.DateField(default=datetime.now()) t_sum = models.FloatField(default=0.0) def __unicode__(self): return str(self.id) class TransactionDetail(models.Model): product …

Django post_save preventing recursion without overriding model save() Question: There are many Stack Overflow posts about recursion using the post_save signal, to which the comments and answers are overwhelmingly: “why not override save()” or a save that is only fired upon created == True. Well I believe there’s a good case for not using save() …

How to use Django model inheritance with signals? Question: I have a few model inheritance levels in Django: class WorkAttachment(models.Model): “”” Abstract class that holds all fields that are required in each attachment “”” work = models.ForeignKey(Work) added = models.DateTimeField(default=datetime.datetime.now) views = models.IntegerField(default=0) class Meta: abstract = True class WorkAttachmentFileBased(WorkAttachment): “”” Another base class, but …

django post_save signals on update Question: I am trying to set up some post_save receivers similar to the following: @receiver(post_save, sender=Game, dispatch_uid=’game_updated’) def game_updated(sender, **kwargs): ”’DO SOME STUFF HERE”’ MyPick.objects.filter(week=game.week, team=game.home_team).update(result=home_result) MyPick.objects.filter(week=game.week, team=game.away_team).update(result=away_result) @receiver(post_save, sender=MyPick, dispatch_uid=’user_pick_updated’) def update_standings(sender, **kwargs): ”’DO STUFF”’ The first receiver is getting called correctly after an update on the Game object, …