Getting a column from an array in jinja2 python

Question

I have an array

{% set myarray = [['apple', true, false],
['banana', false, true]] %}

I want to get

['apple', 'banana']

why is something easy so hard with jinja?

Answer 1

You can use the do extension for jinja2

The “do” aka expression-statement extension adds a simple do tag to the template engine that works like a variable expression but ignores the return value.

Python

from flask import Flask

app = Flask(__name__)
app.jinja_env.add_extension('jinja2.ext.do')

HTML

{% set myarray = [['apple', true, false],['banana', false, true]] %}
{% set second_array = [] %}

{% for a in myarray %}
    {% do second_array.append(a[0]) %}
{% endfor %}

{{ second_array }}

Another way you can do this, without using the do extension, is to generate a custom filter and use standard list comprehension

Python

def get_nth(lst, i):
    return [l[i] for l in lst]
app.jinja_env.filters['get_nth'] = get_nth

HTML

{{ myarray|get_nth(0) }}