jinja2 how to remove trailing newline

Question

I'm using jinja 2 to output a yaml file but can't seem to get rid of a trailing newline and the end of a for loop. Eg the below

 - request:
        path: {{ path }}
        headers:
          origin: 'somedomain.com'
          user-agent: 'agent'
          referer: 'some.domain.com'
          authority: 'somedomain.com'
        querystring:
          {% for key, value in querystring.items() -%}
          {{ key }}: '{{ value }}'
          {% endfor %}
      response:
        content:
          file: {{ content }}

gives me the output:

- request:
    path: /some/path
    headers:
      origin: 'somedomain.com'
      user-agent: 'agent'
      referer: 'somedomain.com'
      authority: 'somedomain.com'
    querystring:
      postcode: 'xxxxxx'
      houseNo: '55'

  response:
    content:
      file: address.json

With an additional unwanted blank line after houseNo. How do I get rid of this line?

score 92 · Accepted Answer · edited Sep 28 '21 at 02:41

92

Change your loop to strip whitespace from the top AND bottom of the output (notice extra - at the for loop close):

{% for key, value in querystring.items() -%}
  {{ key }}: '{{ value }}'
{%- endfor %}

In my tests (using https://github.com/abourguignon/jinja2-live-parser), the - must come after the first {%, not before the last to achieve what you're asking for.

Docs: https://jinja.palletsprojects.com/en/latest/templates/#whitespace-control

edited Sep 28 '21 at 02:41

ggorlen

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answered Apr 26 '16 at 17:01

tknickman

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Yeah, you are right. Prepending the `-` instead of appending preserves the indentation and does not screw up the spaces in the next line. – alecxe Apr 26 '16 at 17:09
Correct, I didn't remember this detail until I played around with it again. – tknickman Apr 26 '16 at 17:11
27

For me, this puts all the key: value pairs on a single line. I don't understand why this answer was accepted. – Honza Sep 30 '16 at 09:19
6

Just because I didn't see this part of the explanation anywhere, I figured I'd add it. Putting a `-` before the second percent sign on the first line of the for loop removes newlines before the added line. Putting a `-` after the first percent sign on the last line of the for loop removes newlines after the added line. Combine them both, and you get 0 newlines. Have only one, and you only get a newline to separate a line, but not an extra newline between each line. In my case, I wanted a newline before the loop but not after each element, so I put the `-` before the `endfor`. Hope this helps – dddJewelsbbb Nov 19 '18 at 16:52

score 20 · Answer 2 · edited Jun 08 '21 at 16:19

20

I think you can get rid of it using the whitespace control feature. Thus I would modify the endfor block to {% endfor -%}

See if that does it!

edited Jun 08 '21 at 16:19

Josh Kelley

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answered Apr 26 '16 at 17:01

Scratch'N'Purr

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score 11 · Answer 3 · answered Jan 13 '19 at 00:03

11

For those using Flask who arrive here, these lines did the trick for me:

app = Flask(__name__)
app.jinja_env.lstrip_blocks = True
app.jinja_env.trim_blocks = True

answered Jan 13 '19 at 00:03

MarredCheese

13,598
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3

Maybe you could make your answer more generic by explaining that you can set it in the Environment object: `Environment(trim_blocks=True, lstrip_blocks=True)` – Adrien H Apr 01 '19 at 07:54

Zhou Shuai-Ming · Answer 4 · 2016-08-16T15:05:45.120

6

I found a way to solve this problem:

- request:
    path: {{ path }}
    headers:
      origin: 'somedomain.com'
      user-agent: 'agent'
      referer: 'some.domain.com'
      authority: 'somedomain.com'
    querystring: >-
      {% for key, value in querystring.items() -%}
      {{ key }}: '{{ value }}'
      {% endfor %}
  response:
    content:
      file: {{ content }}

>, |: "clip": keep the line feed, remove the trailing blank lines.
>-, |=: "strip": remove the line feed, remove the trailing blank lines.
>+, |+: "keep": keep the line feed, keep trailing blank lines.

Thx Steve Bennett's post: In YAML, how do I break a string over multiple lines?

edited Aug 16 '16 at 15:05

answered Aug 16 '16 at 14:55

Zhou Shuai-Ming

103
1
4

1

Thanks for this, helped me fix my issue, how ever the correct operator i had to use is "|-" (pipe minus), now my multi line string is correctly transported to my json files, with all line ending except the last one. – diegeelvis_SA Aug 17 '18 at 11:06

score 3 · Answer 5 · answered Nov 09 '20 at 11:56

The accepted answer is only half of the solution, because it removes all newlines.

You can avoid the trailing newline by first removing all newlines (using the minus signs at -%} and {%- in the for loop), and then inserting the desired newlines at the right place (using the loop.last condition).

The following templates renders a dictionary, d, to as JSON text:

{
    {% for key, value in d.items() -%}
    "{{ key }}": "{{ value }}"{{ ",
    " if not loop.last }}
    {%- endfor %}
}

For d = {'a':'1', 'b':'2'}, the template renders to

{
    "a": "1",
    "b": "2"
}

spacether · Answer 6 · 2021-05-27T18:39:21.713

You can suppress rendering of the below lines:

<% for ... %>
<% endfor %>
<% if ... %>
<% endif %>

by setting trim_blocks=True and lstrip_blocks=True in your jinja2 environment. See the example below, info from their docs

context = {'querystring': querystring, 'path': path, 'content': content}    
jinja_env = jinja2.Environment(
    loader=jinja2.FileSystemLoader('templates/'),
    trim_blocks=True,
    lstrip_blocks=True
)
print(jinja_env.get_template('my_template.yaml').render(context))

jinja2 how to remove trailing newline

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