How to remove brackets from Jinja list variable (DBT) - jinja2

Question

I have a list variable created like this: {% set options = ["a", "b", "c"] %}
I want to use it in a SQL CTE like this:
df as (
select *
from my_table
pivot (sum(value) for option in ({{options}}))
)
When the SQL is compiled by DBT, the result is:
df as (
select *
from my_table
pivot (sum(value) for option in (["a", "b", "c"]))
)
And that won't work because of the brackets. So how can I use the list variable without including the brackets?

Answer 1

#larsks is right that you want to create a string from your list, not change the way the list is displayed.
The easiest way to do this is to use the join filter in jinja:
{% set options = ["a", "b", "c"] %}
{{ options | join(", ")}}
-- compiles to:
a, b, c
That works fine for numbers, but to get string literals into your sql query, you'll need to quote the values in your list. I prefer to do this by adding nested quotes in the list itself:
{% set options = ["'a'", "'b'", "'c'"] %}
{{ options | join(", ")}}
-- compiles to:
'a', 'b', 'c'
But you can also put the extra quotes inside the argument to join, and concatenate an extra quote to the beginning and end of your string:
{% set options = ["a", "b", "c"] %}
{{ "'" ~ options | join("', '") ~ "'"}}
-- compiles to:
'a', 'b', 'c'
Or you can wrap you jinja expression in a single quote to achieve the same thing, but I think this is hard to read::
{% set options = ["a", "b", "c"] %}
'{{ options | join("', '") }}'
-- compiles to:
'a', 'b', 'c'

Answer 2

You're asking for the string representation of a list variable; that's always going to include the brackets. If you want something different you need to take a more active role in formatting the data.
The general recommendation for this sort of thing is to format the string in your code before rendering the template. E.g:
import jinja2
options = ["a", "b", "c"]
template = jinja2.Template('''
df as (
select *
from my_table
pivot (sum(value) for option in ({{options}}))
)
''')
print(template.render(options=', '.join(f'"{x}"' for x in options)))
If you can't do that, here's on option:
import jinja2
template = jinja2.Template('''
{%- set options = ["a", "b", "c"] -%}
{%- set comma = joiner(", ") -%}
df as (
select *
from my_table
pivot (sum(value) for option in ({% for option in options %}{{ comma() }}"{{ option }}"{% endfor %})
)
''')
print(template.render())
Which outputs:
df as (
select *
from my_table
pivot (sum(value) for option in ("a", "b", "c")
)

Answer 3

As a workaround I ended up changing my Jinja variable to a tuple like this:
{% set options = ("a", "b", "c") %}
I will select one of the other answers as the best answer.