CODEWITHSUNDEEP
python
John
John

Reputation: 79

Python 'none' acting weird from one version to another

I'm working on an open source project. Python was upgraded, I THINK from 2.5 to 2.6, and this problem came up.

get_custom_fields(self.env) was called. self.env was None.

def get_custom_fields(self, customfield=None):
        if not customfield:   
            ...
        else:                 
            ...

Previously this worked fine, and the 'if not' part went through. After the upgrade though, the else started going instead. After removing the self.env, it again goes through the first part. This fixes the problem, but I'm curious why this happened. Did the python upgrade change how optional arguments handle None for some conditionals?

Upvotes: 0

Views: 103

Answers (2)

Florian Mayer
Florian Mayer

Reputation: 3081

Although None is still false, it is always recommended to compare to it using is for performance and correctness reasons (i.e. if foo is None).

Upvotes: 1

Fred Foo
Fred Foo

Reputation: 363767

Did the python upgrade change how optional arguments handle None for some conditionals?

No. None is still false. Check the value of self.env, it might have been set in a way that relied on implementation details. Someone may have compared strings with is instead of ==, for example.

Upvotes: 0

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