passing an argument to a custom save() method

Question

How do I pass an argument to my custom save method, preserving proper *args, **kwargs for passing to te super method? I was trying something like:

form.save(my_value)

and

def save(self, my_value=None, *args, **kwargs):

   super(MyModel, self).save(*args, **kwargs)

   print my_value

But this doesn't seem to work. What am I doing wrong?

Edit: I found this example (see the last message, for passing 'reorder'): http://groups.google.com/group/django-users/browse_thread/thread/b285698ea3cabfc9/6ce8a4517875cb40?lnk=raot

This is essentially what I am trying to do, but my_value is said to be an unexpected argument for some reason.

Defined method `save(self, my_value=None, *args, **kwargs)` expects keyword argument: `save(my_value=some_value)` (check this question about [positional and keyword arguments](https://stackoverflow.com/questions/9450656/positional-argument-v-s-keyword-argument/57819001#57819001)) — Denis, Jul 11 '21 at 09:22

Daniel Naab · Answer 1 · 2010-03-29T02:40:34.687

26

Keyword arguments must follow the positional arguments. Try this instead:

def save(self, my_value, *args, **kwargs):
    ....

or:

def save(self, *args, **kwargs):
    my_value = kwargs.pop('my_value', None)

edited Mar 29 '10 at 02:40

answered Mar 29 '10 at 02:26

Daniel Naab

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Doesn't seem to do the trick - python says it's a syntax error – Nikita Mar 29 '10 at 02:34

score 5 · Answer 2 · edited Sep 26 '20 at 11:39

5

You can try the following.

Override the save method as:

def save(self, my_val, *args, **kwargs):
    print my_val
    # do_something here
    return super(MyModel, self).save(*args, **kwargs)

On calling the save method as:

MyModel.save(my_val="fooooo")

this will print my_val and save it.

edited Sep 26 '20 at 11:39

ImportError

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answered Aug 29 '12 at 11:01

ashish singh

146
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score 3 · Answer 3 · answered Nov 04 '19 at 16:31

The existing answers are incomplete.

The problem with Model.save is that there are multiple ways to get to it, most notably through Model.objects.create(). A queryset create() call will not pass additional arguments to Model.save and your code might not behave as expected.

You can easily see the source code for create() and other methods (get_or_create, update_or_create) here: https://github.com/django/django/blob/2.2.7/django/db/models/query.py#L415

The bulk_create method of QuerySet does not call save at all. Which means any custom logic will be entirely ignored.

Because of these risks I would consider the premise of the question an anti-pattern to be avoided. Rather than overloading the built in save method, create an entirely different (factory) method to encompass your special behavior e.g. mymodel.special_save().

passing an argument to a custom save() method

3 Answers3

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