Use a parameter attribute as a default value for another parameter?

Question

Is there way in python to set the default value of a parameter to a property of another parameter?

eg

I currently have a function in django which I would like to do

def supplier_default_product(region, supplier=region.default_supplier.id):
    default_product_instance = Product.objects.get(name=default_product, supplier=supplier)
    ....

so that I can call it with either no supplier where it just uses the regions default supplier:

supplier_default_product(region)

or with a specified supplier:

supplier_default_product(region, supplier)

Morgan Thrapp · Accepted Answer · 2015-11-30 19:53:14Z

2

Use None as the default argument and then check in the body of the function for None.

def supplier_default_product(region, supplier=None):
    if supplier is None:
        supplier = region.default_supplier.id
    default_product_instance = Product.objects.get(name=default_product, supplier=supplier)

You can't reference an attribute of another argument, because the default argument values are set at define time, which only happens once.

answered Nov 30, 2015 at 19:53

Morgan Thrapp

10k3 gold badges50 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Yunti Over a year ago

Thanks for the explanation of why it doesn't work too.

Morgan Thrapp Over a year ago

@Yunti No problem. Glad I could help!

Collectives™ on Stack Overflow

Use a parameter attribute as a default value for another parameter?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related