CODEWITHSUNDEEP
djangodjango-modelsdjango-queryset
EarlyCoder
EarlyCoder

Reputation: 1313

Django How to dynamically lookup fields

I would like to do something like this:

before = [ rec.field for rec in all_relevant_records ]

# Do some operation on the all_relevant_records:
for rec in all_relevant_records:
    rec_pk = rec.pk
    new_field = get_new_field(rec, field)
    db.objects.filter(pk=rec_pk).update(field=new_field)

after = [ rec.field for rec in all_relevant_records ]

But, this does not work as field cannot be resolved into a queryset field.

I have looked at How to dynamically provide lookup field name in Django query? But, this is not quite what I want.

Any help appreciated

Upvotes: 2

Views: 1275

Answers (1)

Antoine Pinsard
Antoine Pinsard

Reputation: 35002

When you do:

db.objects.filter(pk=rec_pk).update(field=new_field)

you are using keyword arguments. Which is equivalent to:

db.objects.filter(**{'pk': rec_pk}).update(**{'field': new_field})

so if field is not the name of your field, but a variable containing the name of your field, what you want to do is:

db.objects.filter(pk=rec_pk).update(**{field: new_field})

About this:

before = [ rec.field for rec in all_relevant_records ]

I'm not sure what you are trying to achieve, but I guess it should be something like this:

before = [getattr(rec, field) for rec in all_relevant_records]

Upvotes: 2

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