CODEWITHSUNDEEP
djangopython-3.xdjango-modelsdjango-migrations
Eternal
Eternal

Reputation: 933

Django ignores model field

So, I came across this when I was working on a project.

I had mistakenly placed a "," after a field in one of my models and Django did all the migrations while ignoring that particular field. It took me a while to realize that a little "," after the field is responsible for my field not being reflected in the database.

However, I understand that there shouldn't be a coma but I was kind of expecting Django to give me an error or at least a warning.

Something like maybe: "Invalid syntax in models.py near FieldName"

EDIT: "one or more model fields are stored as tuple/s are you sure you want to do so?"

But it ignores that particular field and keeps on migrating. My question is why does Django let that happen? Is this the expected behaviour and shouldn't Django notify for such things? or why this is being passed silently.

Here is an example to have a look at.

class person(models.Model):
    name = models.CharField(max_length=10)
    surname = models.CharField(max_length=10),
    age = models.PositiveIntegerField()

Now, if you create migrations and apply them Django will simply ignore the surname field here and apply the migrations without any errors, why is it so?

Upvotes: 1

Views: 408

Answers (1)

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477607

It is not invalid syntax. By adding a trailing comma, you wrap the field in a singleton tuple. So the type of person.surname is tuple.

For example if you write:

>>> a = 1,
>>> a
(1,)
>>> type(a)
<class 'tuple'>

A model can, besides the model fields contain all sorts of things: constants, subclasses, methods, etc.

One could do an exhaustive search in all the fields, etc. to check if a tuple wraps a model field, but that could take considerable time, it might result in evaluating lazy attributes, and it might even get stuck in an infinite loop.

It might however be something that can be added to flake8-django [GitHub].

Upvotes: 2

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