python print jinja2 rendered output in json format

user_14752209 0
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my variable file/data (i get this info from other source)

final_lst:

[
  {
    "service_role": "do_not_use",
    "first_ip": "10.7.17.1",
    "last_ip": "10.7.16.9",
    "uid": "do_not_use"
  },
  {
    "service_role": "role_a",
    "first_ip": "10.7.17.10",
    "last_ip": "10.7.17.25",
    "uid": "role_a_range_01"
  },
  {
    "service_role": "role_a",
    "first_ip": "10.7.17.56",
    "last_ip": "10.7.17.70",
    "uid": "role_a_range_02"
  }
]

test.j2:

{%- for item in final_lst %}
sr: {{item.service_role}}
ip: {{item.first_ip}}
{%- endfor -%}

my code: from jinja2 import Template , Environment, FileSystemLoader

env = Environment(loader=FileSystemLoader('templates'),)
int_template = env.get_template('test.j2')     

out = int_template.render(final_lst=final_lst)
print(out)

result:

sr: do_not_use
ip: 10.7.17.1
sr: role_a
fip: 10.7.17.10
sr: role_a
fip: 10.7.17.56

what i want to print is in json format like below

desired output:

[
  {
    "sr": "do_not_use",
    "fip": "10.7.17.1"
  },
  {
    "sr": "role_a",
    "fip": "10.7.17.10"
  },
  {
    "sr": "role_a",
    "fip": "10.7.17.56"
  }
]

i have a requirement to generate above output via jinja2 template. how can i get json format output anything that is rendered from jinja2 template

jinja2 python-3.x python json
1 Answers

I'd suggest not to generate json with means of template language. It is slower and much more error prone.

In your python code:

import json
from jinja2 import Template, Environment, FileSystemLoader

data = [
  {
    "service_role": "do_not_use",
    "first_ip": "10.7.17.1",
    "last_ip": "10.7.16.9",
    "uid": "do_not_use"
  },
  {
    "service_role": "role_a",
    "first_ip": "10.7.17.10",
    "last_ip": "10.7.17.25",
    "uid": "role_a_range_01"
  },
  {
    "service_role": "role_a",
    "first_ip": "10.7.17.56",
    "last_ip": "10.7.17.70",
    "uid": "role_a_range_02"
  }
]
data = [
    {
        'sr': elem['service_role'],
        'fip': elem['first_ip'],
    }
    for elem in data
]
data_dump = json.dumps(data, indent=2)

env = Environment(loader=FileSystemLoader('templates'),)
int_template = env.get_template('test.j2')     

out = int_template.render(data_dump=data_dump)
print(out)

In your template (test.j2):

{{ data_dump }}

Don't do this!

If you insist on template solution:

[
  {% for item in final_lst %}
  {{ '{' }}
    "sr": "{{ item.service_role }}",
    "ip": "{{ item.first_ip }}"
  {{ '}' }}
  {% endfor %}
]

You can replace {% with {%- back to get compact representation (same applies to json.dumps, just get rid of indent parameter).

user_144011600
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