raise an exception in jinja if we passed in a variable that is not present in the template

Question

Is there a method for jinja2 to raise an exception when we pass a variable that is not present in the template?

PS: This is different(or opposite) from raising an exception when a variable is present in the template but it is not passed. For this I use "undefined=StrictUndefined"

score 50 · Answer 1 · answered Jul 03 '12 at 16:47

50

When you load your jinja2.Environment, set the 'undefined' parameter to 'jinja2.StrictUndefined', e.g.:

env = jinja2.Environment(loader=<someloader>, undefined=jinja2.StrictUndefined)

You can catch and examine the render exception to see what was missing

EDIT It would help if I read your full question. :)

answered Jul 03 '12 at 16:47

Jon McKenzie

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Not an answer to the OP but just what I was looking for (and what most users are looking for, judging by the upvotes). – Jérôme Oct 20 '21 at 13:24
came here to upvote the wrong answer because it was my right answer – mukunda Feb 03 '23 at 21:57

score 16 · Answer 2 · edited Jun 24 '20 at 21:08

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Maybe this could help you https://jinja.palletsprojects.com/en/2.11.x/api/#the-meta-api

>>> from jinja2 import Environment, meta
>>> env = Environment()
>>> ast = env.parse('{% set foo = 42 %}{{ bar + foo }}')
>>> meta.find_undeclared_variables(ast)
set(['bar'])

edited Jun 24 '20 at 21:08

dom1310df

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answered May 31 '11 at 03:24

sacabuche

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Maoz Zadok · Answer 3 · 2021-04-07T08:26:34.370

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You can also do that:

from jinja2 import Template, StrictUndefined
Template('name: {{ name }} , city: {{ city }}',undefined=StrictUndefined).render(**{"name":"foo","city":"bar"})

edited Apr 07 '21 at 08:26

answered Jan 26 '21 at 15:51

Maoz Zadok

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Excellent. Complements the `Environment` response. We use the one to discover the tokens but the other to actually render the content. – Dustin Oprea Feb 02 '22 at 04:54

raise an exception in jinja if we passed in a variable that is not present in the template

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