Template Variables Docs Incorrect/Unclear

[tom.dalton@…]

On this section ​https://docs.djangoproject.com/en/1.6/topics/templates/#variables
In the "Behind the Scenes" section, it gives the order that Django tries to resolve a variable like "X.Y".
The 4 things that it tries are accurate, but the way/order they're done doesn't appear to be correct.

Ref the code that does this:
​https://github.com/django/django/blob/master/django/template/base.py#L756

What actually (seems to) happen is:

• Try dictionary lookup to get "thing"
• If not found "thing", try attribute lookup to get "thing"
• If not found "thing", try list-index lookup to get "thing"
• If not found "thing", then fail
• If "thing" is callable, then "thing" = "thing()"
• Return "thing"

Applies in version 1.6 and onwards, probably applicable to older doc versions too.

[Baptiste Mispelon]

Hi,

It seems this list has remained largely unchanged since its initial introduction (096ad32c845f850278b942d087e607dc4311b5f9).

I don't see a reason to distinguish argument lookups and method calls. I think we could simply merge the two items into one: "Attribute/method lookup".

THanks

[anonymous]

Even that's not quite accurate, since it tries the initial lookup (dict then attribute then list index). Once it's got that value, it then calls it if possible.

So maybe the docs should say something like:

Value lookup is done in the following order:

• dict-key
• attribute
• list-index

If the value is callable, it is called, and the value becomes the result of that call.

[tom.dalton@…]

So I guess I'm saying there are 2 issues:

1. The Attribute lookup vs Method call thing.
2. It's not stated that other values (e.g. if dictionary or list lookup worked) are actually called. The docs imply only methods are called.

[Baptiste Mispelon]

Yes, good point.

[Gabriel Muñumel]

Here is the pull request ​https://github.com/django/django/pull/2994.

[anonymous]

Thanks for that. I added a comment to the pull request with a patch for a slightly more comprehensive rework to include the stuff talked about enough. I don't think that just combining attribute/method lookup is enough to clarify what Django actually does behind the scenes.

[Baptiste Mispelon <bmispelon@…>]

In 62c74abbb06a081708c2cb5cc459f39beb26acaa:

Fixed #23114 -- Clarified documentation of template lookups.

Thanks to gmunumel and Tom Dalton for their help on the patch.

[Baptiste Mispelon <bmispelon@…>]

In 13d44f54a265e9fc6185e1d5518da8ad568fbaad:

[1.7.x] Fixed #23114 -- Clarified documentation of template lookups.

Thanks to gmunumel and Tom Dalton for their help on the patch.

Backport of 62c74abbb06a081708c2cb5cc459f39beb26acaa from master.

[anonymous]

Thanks for the speedy resolution!