Question

I noticed that you can’t have -, +, /, *, or any other mathematical character symbol in the related_name. You also can’t use :, |, or ..

If you have any of the above characters in related_name, although Django’s models.py will validate, whenever you do a query lookup it’ll throw an error like

Q(userprofile.user__place__managers=user)
SyntaxError: keyword can't be an expression

The reason I want to use a special character is because I like to have my related_name in the form of {class_name}{field_name}. So for example for the UserProfile model class I would do something like

class UserProfile(models.Model)
    user = models.OneToOneField(User, related_name='userprofile-user')
    user_type = models.ManyToManyFields(UserType, related_name='userprofile-user_type')

That way when I do a query that involves a following a relationship backward, but still know how I am following it backward. For example, if I simply do

user_type = models.ManyToManyFields(UserType, related_name='user_type')

then I can access UserType from User doing User.objects.get(pk=1).user_type.all(). But this makes it looks like user_type is a field of User.

Instead if I could do something like User.objects.get(pk=1).userprofile-user_type.all() then I would know that I am going from User to UserProfile to UserType.

Well my way of thinking is probably in the minority and I would assume that most people would just do related_name='user_type' or maybe even use default user_type_set.

Another question would be: What is the good style for naming related_name?

Answer 1

userprofile-user_type is not a valid python identifier.

Python thinks you are trying to subtract user_type from userprofile.

In your specific case profiles would be a good enough related manager name.

So that when you have a a UserType instance:

utype = UserType.objects.get(...)
utype.profiles.all()

It would give you all the profiles associated with that user type.

Also there is no ManyToManyField*s*, remove the “s”.

Try not to be more verbose than what is needed to convey the meaning of a relationship.
The field name inside the related name is redundant and unnecessary.

UPDATE:
Please do not name it userprofiles_from_user_type

It’s like having this:

class Person:
    def PersonWalk(self):
        ...

Instead of:

class Person:
    def walk(self):
        ...

Let me give you a more complex example with an intermediate table

class Service(Model):
    name = models.CharField(max_length=32)

class Person(Model):
    services = models.ManyToManyField('self', through='PersonServiceRel', null=True, related_name='friends', symmetrical=False)

class PersonServiceRel(Model):
    provider = models.ForeignKey(Person, related_name='provided_services')
    consumer = models.ForeignKey(Person, related_name='consumed_services')
    service = models.ForeignKey(Service)

Now let’s say we have people providing some kind of services to each other and I want
to know if the user “rantaplan” provides “tracking” service and to whom.

rantaplan = Person.objects.get(name='rantanplan')
tracking = Service.objects.get(name='tracking')
PersonServiceRel.objects.filter(provider=rantaplan, service=tracking)
# or
rantaplan.provided_services.filter(service=tracking)

Note the PersonServicesRel the fields ‘provider’ and ‘consumer’ and their related_manager.
Also note the necessary query. I think it’s quite readable.

So I suggest that you name your fields and related managers depending on their purpose and usage, with as little verbosity as possible.