Django model method paramter with default value from related

Question

I need a model method with parameter with default value:

class MyModel(models.Model):
    parameter1 = models.DecimalField(max_digits=8,decimal_places=6, default=0)

    def my_method(self, parameter = parameter1)
        return parameter

But it doesn't work

Ideas?

Does this answer your question? assigning class variable as default value to class method argument — Nick ODell
– Nick ODell, Commented Oct 19, 2022 at 23:06
The short version is that Python evaluates the value of a default variable once, when the method is defined, not when the method is executed. So having a default value from the class is not possible. The next best thing is to have it default to None and replace None with the value you want. — Nick ODell
– Nick ODell, Commented Oct 19, 2022 at 23:08
@NickODell great explanation! Now everything is perfectly clear — Tomasz Brzezina
– Tomasz Brzezina, Commented Oct 21, 2022 at 8:52

Nealium · Accepted Answer · 2022-10-20 01:13:01Z

1

read @Nick ODell's comment, he's much smarter than me

but just add a little if!

class MyModel(models.Model):
    parameter1 = models.DecimalField(max_digits=8,decimal_places=6, default=0)

    def my_method(self, parameter = None)
        if parameter != None:
            return parameter
        return self.parameter1

        # or if you don't plan on passing 0 (zero)
        return parameter if parameter else self.parameter1

answered Oct 20, 2022 at 1:13

Nealium

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1 Comment

Tomasz Brzezina Over a year ago

I did it in my code, but I was hoping to make it simplier. But now I hope it helps other noobies ;D

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