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Why context=None ?

on 4/13/15, 11:20 AM 824 views

My question is bit pythonic. but I am curious to know the answer.

I have seen in method Odoo is passing context=None. like

def create(self, cr, uid, vals, context=None):
     if not context: context = {}

Why they have not used context={}? like

def create(self, cr, uid, vals, context={}):

can anyone shade light on it?

On 6/16/15, 3:40 AM

Because {} is mutable and None is immutable.

Mutable default values are awkward: if you change the value in you function it will also change the *default* value for all later calls of your function.

See https://doc.odoo.com/contribute/15_guidelines/coding_guidelines_framework/#the-infamous-context

The lengthy discussion about that here: https://bugs.launchpad.net/openobject-addons/+bug/525808

On 4/14/15, 2:58 AM

This notation in python mean that context is a optionnal arg of the function. If no context is given, context is equal to none.

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Asked: 4/13/15, 11:20 AM
Seen: 824 times
Last updated: 6/16/15, 3:40 AM