How to extend a dict in Jinja?

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1

Hi, I want to use the „do“ statement in jinja templating, particularly in a markdown card for lovelace.
It seems like the jinja2.ext.do extension has to be used. How can I add this extension?

Updated, more appropriate question: How to extend a dict without do statement?

1 Like
2

It’s not possible without forking home assistant.

3

Why do you want this anyways? Chances are, you don’t need it. Can you explain your use case?

4

Hi, thanks for your answer! I want to add new key/value pairs to dictionaries. Precise use case is sorting dates and corresponding events. Sure, it should somehow be possible without dicts, but this seemed to me most elegant. I figured out how to sort given dicts by key or by value. But I can’t define a static dict, I want to add entries based on conditions. I tried some things for adding key/value pairs, but all failed. Here is what I tried from this site so far and what errors I got:

{% set data  =  {} %}
{%- set _ = data.update({'new_key': new_value}) -%}

Gives: SecurityError: access to attribute 'update' of 'dict' object is unsafe.

{% set _ = data.__setitem__('new_key', new_value) %}

Gives: SecurityError: access to attribute '__setitem__' of 'dict' object is unsafe.

Similarly, I could start with a full dict and delete items using data.pop(), but this gives me the same SecurityError.

Then I found a python-like option using ‘do’:

{%- do data['new_key'] = new_value -%}

Or in the same flavour as the first attempt, without getting a returned value:

{%- do data.update({'new_key': new_value}) -%}

The 'do' statements give me: "TemplateSyntaxError: Encountered unknown tag 'do'." So my idea was to add this extension, but unfortunately, this is not possible.

How is it possible to add key/value pairs to dicts? Or why isn’t it? Why is a SecurityError thrown? It seems that manipulating dictionaries is blocked. Can I unblock those commands manually?

5

make a list of kevalue pairs:

{% set kvps = [('x', 1), ('y',1)] %}

then create your dictionary. You will not be able to update an existing dictionary with .update({})

{% set data = dict.from_keys(kvps) %}

Your best option to ‘update’ an existing dictionary (current) with another dictionaries values (update)…

{# make current a list of tuples #}
{% set current = current.items() | list %}
{# make update a list of tuples #}
{% set update = update.items() | list %}
{# remove keys from current that are in update #}
{% set current = current | rejectattr('0', 'eq', update | map(attribute='0') | list) | list %}
{{ dict.from_keys(current + update) }}

EDIT: This method restricts you from using dictionary keys that start with a number and have whitespace. Keep that in mind.

7 Likes
6

Thank you so much, that worked! I do not necessarily need to change the dict once it is created (but I learned a lot from your example). Instead, I can iteratively build the list and then create a dict from it, like this:

{% set kvps = [('x', 4), ('y',2)] %}
{% set kvps = kvps + [('z', 1)] %}
{% set data = dict.from_keys(kvps) %}
2 Likes
7

Actually, I don’t need a dict at all. One can also sort the list by key or by value. In case anybody needs it some day:

Sorting the list of key-value pairs by key:

{%- for key, value in kvps|sort(attribute='0') -%}
  {{ key }}: {{ value }}
{% endfor %}

Gives

x: 4
y: 2
z: 1

Sorting the list of key-value pairs by value:

{%- for key, value in kvps|sort(attribute='1') -%}
  {{ key }}: {{ value }}
{% endfor %}

Gives

z: 1
y: 2
x: 4
2 Likes
8

This can be easily done by creating a new dict in this way:

{% set my_dict = dict(a=1, b='b') %}
{% set my_dict = dict(my_dict.items(), a="one", c=3.14) %}

Which correctly generates:

{'a': 'one', 'b': 'b', 'c': 3.14}
1 Like
9

That method does not allow for variable key names unless you provide 2 dictionaries.

EDIT: 2 dict method…

{% set my_dict = dict(my_dict.items(), **otherdict) %}
1 Like
10

thanks! after a long search for a solution, this finally helped me solve my problem.

for anyone coming across the same problem: any of these two can be used to filter the attributes of an entity in a template, to only return the ones required.

for example on a weather entity:

{{ dict(states.weather.weather.attributes|items|rejectattr('0', 'in', 'supported_features, precipitation_unit, wind_speed_unit, visibility_unit, pressure_unit, temperature_unit, friendly_name, attribution')) }}

definitely not the most elegant solution, but it was the only one that worked for me.