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:

1. http://cewing.github.io/training.codefellows/assignments/day22/jinja2_walkthrough.html
2. In Jinja2 whats the easiest way to set all the keys to be the values of a dictionary?
3. https://github.com/saltstack/salt/issues/27494

Answer 1

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.

UPD: Also, this works for len() (__len__()), str() (__str__()), repr() (__repr__()) and many similar things.

Answer 2

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

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

or

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

Answer 3

Key takeaways:

1. dictionary does not support append().

2. You can add the new item to the data dictionary by using {% do ... %} tag as shown here:

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

3. However, for the "do" tag to work properly you need to add the jinja2.ext.do extension to your jinja Environment.

Answer 4

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