In this blog post, I will show how we can add to_toml filter to Ansible template filters. This filter can be very helpful in situations where we want to generate config files that are in TOML format. TOML is a file format very similar to JSON and YAML. You can read more about this format here: We will use Ansible filter plugins to implement our new filter.


Let’s start with a simple Ansible playbook file where we define our configuration variables.


- name: Test Yaml
  hosts: localhost
    config_data: # this is our config file variable
      x: stringtest
      a: 1
      b: 2
        - test
        - test2
        a: 1
        b: 2
    - template:
        src: config.toml.j2
        dest: config.toml

Next, create a configuration template. Here we are using the to_toml filter that will render our config_data dict from Ansible playbook into TOML representation.


{{ config_data | to_toml }}

The last step is an actual implementation of the to_toml filter. We will start with the installation of the toml python package. You can install the toml package using this command.

pip install toml

Next, create a file named in filter_plugins dir on the same lever where the playbook is located.



import toml
import json

class FilterModule(object):

    def filters(self):
        return {'to_toml': self.to_toml}

    def to_toml(self, variable):
        s = json.dumps(dict(variable))
        d = json.loads(s)
        return toml.dumps(d)

As you can see we are doing some strange thing here. We are converting into string and back to Python dict using python JSON library. We need to do this to provide string in a good format for the YAML parser to be able to work as expected.

s = json.dumps(dict(variable))
d = json.loads(s)

After this operation, all strings inside d dict are in standard Python string format. Without is strings are in <class 'ansible.parsing.YAML.objects.AnsibleUnicode'> format and this will cause TOML rendering to break. For example this

x: stringtest

will be rendered like this

x = [ "s", "t", "r", "i", "n", "g", "t", "e", "s", "t",]

and we do not want that.


After we set up our new filter we can use it like this

ansible-playbook yaml_test.yml

Next check the contents of config.toml

x = "stringtest"
a = 1
b = 2
t = [ "test", "test2",]

a = 1
b = 2

As you can see we got TOML representation of our variable in Ansible Playbook.


In this blog post, I presented how you can render TOML config files using Ansible templates filters. Toml files are getting very popular and a lot of DevOps software is using it for example Now you can start using to_toml filter in order to generate your own TOML configuration files using Ansible.