How to add a new entry into a dictionary object while using Jinja2?

Question

I am not able to append add a new entry into a dictionary object while using jinja2 template.

For example, here I am using jinja2 template and I have created a data variable which is a dictionary. And after checking some if condition I want to append location attribute to the data object, e.g.:

{%- set data = {
                  'name' : node.Name,
                  'id' : node.id,
               }
-%}

{% if node.location !="" %}
    data.append({'location': node.location}) 
{% endif %}

However I could not find a way to achieve this and am getting the UndefinedError:

jinja2.exceptions.UndefinedError: 'dict object' has no attribute 'append'

Has anyone faced this issue or could provide a reference to solve this?

I searched the web but could not find a solution i.e. how to achieve adding an entry to the dict object in the Jinja.

I have referred following and other web resources:

score 30 · Answer 1 · edited Mar 08 '23 at 08:00

30

Without the jinja2.ext.do extension, you can do this:

{% set x=my_dict.__setitem__("key", "value") %}

Disregard the x variable and use the dictionary which is now updated.

This also works for len() (__len__()), str() (__str__()), repr() (__repr__()) and many similar things.

edited Mar 08 '23 at 08:00

β.εηοιτ.βε

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answered Apr 06 '17 at 20:34

Арсений Пичугин

507
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14

hmm, does not work, with ```myString="{% set data={} %}{% set data2=data.__setitem__('key','value') %}{{ data2['key'] }}"; a=Environment(loader=BaseLoader()).from_string(myString); a.render()``` the output is `''` – K. Frank Feb 10 '19 at 00:53
@K.Frank, the answer says to disregard the variable that you assign to. `{% set data={} %}{% set x=data.__setitem__('key', 'value') %}{{ data['key'] }}` – sleblanc May 27 '19 at 22:05
4

I get `access to attribute '__setitem__' of 'dict' object is unsafe` when trying this (Python3, running [dbt](https://www.getdbt.com/)=0.14.2) – dsz Oct 03 '19 at 23:42

score 18 · Answer 2 · edited Mar 08 '23 at 08:02

18

Dictionaries do not have the append method. You can add a key-value pair like this though:

{% do data.update({'location': node.location}) %}

or

{% do data['location']=node.location %}

edited Mar 08 '23 at 08:02

β.εηοιτ.βε

33,893
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answered Apr 27 '16 at 10:10

alpert

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2

Thanks Alpert! Though after using {% do data['location']=node.location %} or {% do data.update({'location': node.location}) %} I still got the TemplateSyntaxError, but after some searching on web I discovered my jinja environment was missing the jinja2.ext.do extention because of which that "do" tag was throwing the syntax error. Now it is working fine :) Thanks again!! – hemant_maverik Apr 28 '16 at 06:27
This link helped as well : http://stackoverflow.com/questions/2703013/how-can-i-modify-merge-jinja2-dictionaries – hemant_maverik Apr 28 '16 at 06:40
10

The first `{% do data['location'] = node.location %}` does not work for me, perhaps because `data['location'] = node.location` is not actually an expression and does not work with `do`, which expects expressions? – Kye W Shi Jan 02 '18 at 20:17

score 14 · Answer 3 · edited Mar 08 '23 at 08:02

14

Without the do extension:

{%- set _ = dict.update({c.name: c}) -%}

Works in base Jinja2 on Python 3, where the __setitem__ solutions give me:

access to attribute 'setitem' of 'dict' object is unsafe

edited Mar 08 '23 at 08:02

β.εηοιτ.βε

33,893
13
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answered Oct 03 '19 at 23:45

dsz

4,542
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FYI - this works well for updating saltstack pillars with jinja 2 prior to state execution with python 3 clients. – Peter M Jan 10 '20 at 20:56

score 13 · Answer 4 · edited Mar 08 '23 at 08:09

13

Key takeaways:

Dictionary does not support append().
You can add the new item to the data dictionary by using the {% do ... %} tag:
```
{% do data.update({'location': node.location}) %}
```
However, for the do tag to work properly you need to add the jinja2.ext.do extension to your Jinja environment.

edited Mar 08 '23 at 08:09

β.εηοιτ.βε

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answered Apr 28 '16 at 06:33

hemant_maverik

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score 3 · Answer 5 · answered Jan 27 '23 at 18:23

3

Without any of the extensions:

{% set d1 = {'a':'b', 'c':'d'} %}
{% set d2 = {'e':'f'} %}

{{ dict(d1, **d2) }}

Basically you merge the two dicts to create a new one. As this doesn't use any extensions, it also works in Home Assistant.

answered Jan 27 '23 at 18:23

palenpet

31
1

How to add a new entry into a dictionary object while using Jinja2?

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