jinja2 how to remove trailing newline

问题:

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?

回答1:

Change your loop to strip white spaces 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: http://jinja.pocoo.org/docs/dev/templates/#whitespace-control

回答2:

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!

回答3:

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

回答4:

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?

回答5:

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))