Ansible: passing a list of objects to a python script

I'm writing an Ansible role using the script module. The script itself is located within the role's files library. The environment variable test_var is located within a YAML file under the group_vars folder of the whole playbook:

---
- name: execute script
  script: python_script.py {{ test_var }}
  args:
    executable: python

This works fine and well if it's only one simple "key=value" kind of parameter, however I'm not sure how should I pass complex items like lists or list of objects to the python script to use it as a python dictionary.

Is there a best practice for this?

The Ansible role above only returns the first item of the list.

The yaml input:

test_var:
  - val:
      something: 1
  - other_val:
    - '1'
    - '2'
    - '3'

The python code:

import sys

i = 0

print('The first argument: ')
print sys.argv[1]
print(' ')

tmp_string = ""

print('Every argument printed out:')
for x in sys.argv:
  if i > 0:
    print x
    tmp_string += x
  i += 1

print(' ')
print('Concatenating together each argument:')
print tmp_string

Results:

changed: [localhost] => {
    "changed": true,
    "rc": 0,
    "stderr": "Shared connection to localhost closed.\r\n",
    "stderr_lines": [
        "Shared connection to localhost closed."
    ],
    "stdout": "The first argument: \r\n[{uval:\r\n \r\nEvery argument printed out:\r\n[{uval:\r\n{usomething:\r\n1}},\r\n{uother_val:\r\n[u1,\r\nu2,\r\nu3]}]\r\n \r\nConcatenateing together each argument:\r\n[{uval:{usomething:1}},{uother_val:[u1,u2,u3]}]\r\n",
    "stdout_lines": [
        "The first argument: ",
        "[{uval:",
        " ",
        "Every argument printed out:",
        "[{uval:",
        "{usomething:",
        "1}},",
        "{uother_val:",
        "[u1,",
        "u2,",
        "u3]}]",
        " ",
        "Concatenateing together each argument:",
        "[{uval:{usomething:1}},{uother_val:[u1,u2,u3]}]"
    ]
}

I'm not sure what to do whit the us at the beginning of every line.

As I see Ansible passes every line of the yaml as a different command line argument, so the first one only contains the first line. I could concatenate these into a single string with a for loop, but I'm not sure how to convert that into a dictionary or something python can use.

Ansible doesn't really provide a great mechanism for passing complex data to the script module. It might be simpler to write your own Ansible module, and then pass your data to it like any other module:

---
- name: run my module
  mymodule:
    someparameter: "{{ test_var }}"
  

Your module can be a Python script with only a little boilerplate on top of your existing code. Here's a very simple template that would support the above example:

#!/usr/bin/python

from __future__ import absolute_import, division, print_function  # NOQA

from ansible.module_utils.basic import AnsibleModule


def main():
    argument_spec = {
      'someparameter': dict(type='list', required=True),
    }

    module = AnsibleModule(argument_spec=argument_spec,
                           supports_check_mode=True)

    result = {'changed': False}
    
    data = module.params['someparameter']
    
    # ...do something with your data here...

    module.exit_json(**result)


if __name__ == '__main__':
    main()

Drop your module into the library directory of your role and you're all set.

You can find more information in the docs:

• https://docs.ansible.com/ansible/2.3/dev_guide/developing_modules_general.html
• https://docs.ansible.com/ansible/latest/dev_guide/developing_program_flow_modules.html

Probably, you need to apply a filter to the variable. Try this:

---
- name: execute script
  script: python_script.py {{ test_var | to_yaml }}
  args:
    executable: python