Update Django Object

Question

I've an object:-

a = Model.objects.get(id=1)

and a dictionary of data attributes of object a.

update_data = {
colA: 1,
colB: 2,
colC: 3,
}

Now, I want to update object a. How can I do it?

Note:- .update() works on queryset, not on the object. Also, I cannot do a.colA=1 because in that case, I've use setattr on each key.

Is there any way that I can update the object directly?

Where does the dictionary come from? You could probably use a form. — Daniel Roseman, Apr 19 '18 at 09:44
have you tried to filter with id and then apply update? i.e. `Model.objects.filter(id=1).update(**update_data)` — Gahan, Apr 19 '18 at 09:45
@DanielRoseman - I've a function which accepts the dictionary and the user object.. — Praful Bagai, Apr 19 '18 at 09:50
@Gahan - I know this, but the question is I've an object. How do I update it? — Praful Bagai, Apr 19 '18 at 09:50
That doesn't answer the question. Where's the dict coming from? Is it being submitted by the user? In which case why don't you use a form? — Daniel Roseman, Apr 19 '18 at 09:51
Yes, initially the data is accepted via form itself and then the data is routed to some function. — Praful Bagai, Apr 19 '18 at 09:52
@DanielRoseman - With due respect, you're being too chatty. This is how I've designed it and I know what I'm doing. The question is not `why`, the question is `how`. — Praful Bagai, Apr 19 '18 at 09:56

score 4 · Answer 1 · edited Jun 17 '23 at 08:01

4

You can use .update() method like this:

Model.objects.filter(id=1).update(**update_data)

or you can update the individual object (iterating in update_data dict), too:

a = Model.objects.get(id=1)

for name in update_data:
    setattr(a, name, update_data[name])

# don't forget to save the object after modifying
a.save()

edited Jun 17 '23 at 08:01

Mundi

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answered Apr 19 '18 at 09:47

Gokhan Sari

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Great answer! But I want to know if there is a quicker way to do this? As we know, the for loop in python is pretty slow. – Wang Honghui Sep 04 '22 at 05:08

score 3 · Answer 2 · answered Apr 19 '18 at 09:49

3

I think you can do

a = Model.object.get(id=1)
a.__dict__.update(update_data)

answered Apr 19 '18 at 09:49

itzMEonTV

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Out of curiosity, Is it the standard way of doing it? – Praful Bagai Apr 19 '18 at 09:53
1

Absolutely No, Then why dont you use standard `setattr` ? You can loops over dict and use that – itzMEonTV Apr 19 '18 at 09:55
@itzMEonTV you need to save the instance too to commit changes in db – Gahan Apr 19 '18 at 09:58

score 2 · Answer 3 · answered Apr 19 '18 at 09:55

For updating directly considering dictionary already constructed, you may filter objects first and then easily update the data, also filter() is faster then get() (*I have tested on small database size)

As you said in comment if you only have object (model instance) and dictionary you can write it as below:

Model.objects.filter(id=a.id).update(**update_data)

The performance result (tested on small db size) In [4]: g = Genres.objects.last()

In [6]: %timeit Genres.objects.get(id=g.id)
518 µs ± 10.9 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

In [7]: %timeit Genres.objects.filter(id=g.id)
74.2 µs ± 807 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)

Update Django Object

3 Answers3