It appears that not everyone knows that in python you can create classes dynamically without metaclasses. I'll show an example of how to do it.
So we've learned how to use custom QuerySet to chain requests:
Article.objects.old().public()Now we need to make it work for related objects:
user.articles.old().public()
This is done using use_for_related_fields, but it needs a little trick. Thing is that in django related managers are initialized without arguments, and our QuerySetManager takes argument - queryset class.
objects = QuerySetManager(MyQuerySet)We have to update QuerySetManager in such a way, that will allow setting queryset as class field:
class QuerySetManager(models.Manager):
use_for_related_fields = True
queryset_class = QuerySet
def get_query_set(self):
return self.queryset_class(self.model, using=self._db)
def __getattr__(self, key):
return getattr(self.get_query_set(), key)In order to use this manager, we have to create a sublcass and set queryset_class:
class MyManager(QuerySetManager):
queryset_class = MyQuerySetIt's not fun to create such class every time. So we'll write a function that does it for us:
def queryset_manager(qs_class):
class Manager(QuerySetManager):
queryset_class = qs_class
return Manager()Now it's enough to write:
objects = queryset_manager(MyQuerySet)Subscribe for the news and updates
This article offers key insights into the ISTQB certification and shares a proven preparation strategy to help candidates succeed.
One of the key requirements for modern UI is being performant. No matter how beautiful your app looks and what killer features it offers, it will frustrate your users if it clangs.
In this article we'll review general approach to working with the best kind of projects - the ones with old untested and undocumented spaghetti code and a tight schedule. We'll review anger management techniques, coping mechanisms and some refactoring tips that might come in handy.
File upload works differently from simple form inputs, which can be somewhat troublesome for beginners. Here I'll show you how to handle uploads with ease.
When we use css-sprites it's important to make browser cache them for longest period possible. On other hand, we need to refresh them when they are updated. This is especially visible when all icons are stored in single sprite. When it's outdated - entire site becomes ugly.
As you know, model managers can be overriden in Django. It's convenient to add custom filtration method.