Question

I have the following Django Model –

class M(models.Model):
    ...
    disp_name = models.CharField(max_length=256, db_index=True)
    ...

class XX(models.Model):
    x = models.ForeignKey(User)
    y = models.ForeignKey(M, unique=True)

Now in my views.py, I want to do a partial string match on all items in XX with the field y.disp_name.

Normally one would do this – M.objects.filter(disp_name__istartswith='string')

But here M is a foreignkey in Model XX. So if I do XX.objects.filter(y.disp_name__istartswith='string') I get an error.

Also, this too fails –
u = User.objects.get(id=1)
u.xx_set.filter(y.disp_name__istartswith='string')

Exception that I get says is – SyntaxError: keyword can't be an expression (<console>, line 1)

How to do this?

Answer 1

I wish you had used proper field names rather than X, Y and M – it’s really hard to follow.

But in any case, you should always use the double-underscore syntax to follow relations on the left hand side of the filter expression:

XX.objects.filter(y__disp_name__istartswith='string')

(The technical reason for this is that the parameters to filter are actually keyword arguments to a function, so the left-hand side of that has to be a string rather than an expression.)