Create a varaible list conditionally from dictionary items

[Javeria Khan]

Hi,

I've tried searching everything but can't find a possible solution. I have a yml that defines all my variables for a playbook and I need to do something like the following inside of it:

----------------

my_dict:

 - {  item_en: True,  name: name1, type:  type1,  key: value1 }

 - {  item_en: False, name: name2, type:  type2,  key: value2 }

 - {  item_en: True,  name: name3, type:  type3,  key: value3 }

my_list:

{%  for item in my_dict %}

{% if my_dict[item].item_en == True %}

    {{ my_dict[item].name  }}

{% endfor %}

---------------

So basically I need 'my_list' to be a list of 'names' from every dict object that has item_en = True. Based on the data structure above, it would look like this:

my_list:

 - name1

 - name3

I know this is possible using the jinja loop syntax in a template but this isn't a template file.

Thanks 

[Matt Martz]

I think you want something like:

my_list: "{{ my_dict|selectattr('item_en')|map(attribute='name')|list }}"

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Matt Martz
@sivel
sivel.net

[Christian Thiemann]

Matt's solution is fine (and elegant!) for simple cases like this particular one. However, I found myself needing to filter items on some more complex conditions a few times and started using the Jinja do extension to effectively turn variable assignments into arbitrary computations:

my_list: |
  {%- set names = [] -%}
  {%- for item in my_dict if item.item_en -%}
    {%- do names.append(item.name) -%}
  {%- endfor -%}
  {{ names }}

It's important to do proper whitespace-control (the dashes in {%- ... -%}) because in the end the string assigned to my_list must be "['name1', 'name3']" and not something like "   ['name1', 'name3']". In the former case, Ansible converts it to a proper list (because the value starts with '['), in the latter my_list would be assigned the actual string "   [...]".

And you need to enable the Jinja extension in your ansible.cfg:

[defaults]
jinja2_extensions = jinja2.ext.do

As mentioned in the beginning, this isn't really necessary in this case and certainly isn't very much in Ansible's spirit of simplicity, but it has saved me from duplicating information across multiple variables several times.

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[Shawn Ferry]

Why not something like this?

do_something_with: item.name

with_items: your_dict

when: item.item_en == True

[Javeria Khan]

Thanks guys, 

Christian is your solution doable in a regular yml? I thought jinja constructs were only allowed in jinja templates? What I have is a regular .yml that defines all my variables.

Shawn I believe your solution requires creating a task to loop over my_dict, I prefer to do it outside of the playbook.

[Javeria Khan]

Also, another quick question. If I was using my_dict in a task loop, could i put a condition on: 

with_items: my_dict

when: item.key is defined

will that work?

[Shawn Ferry]

On Wed, May 20, 2015 at 3:19 PM Javeria Khan <javer...@gmail.com> wrote:

Also, another quick question. If I was using my_dict in a task loop, could i put a condition on: 

Right that is my example. Here it is in code when item_en is false the item is skipped.

TASK: [Loop] ******************************************************************

changed: [127.0.0.1] => (item={'key': 'value1', 'type': 'type1', 'name': 'name1', 'item_en': True})

skipping: [127.0.0.1] => (item={'key': 'value2', 'type': 'type2', 'name': 'name2', 'item_en': False})

changed: [127.0.0.1] => (item={'key': 'value3', 'type': 'type3', 'name': 'name3', 'item_en': True})

https://gist.github.com/shawnferry/572c4f733a3f06f86a37

 

with_items: my_dict

when: item.key is defined

will that work?

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[Christian Thiemann]

Yes, I have that stuff in my group_vars/all and in various vars.yml files. There no special magic to it except that you have to enable the do extension in ansible.cfg.

Every string variable in Ansible is fed through the templating engine:

---

foobar_config_path: "/etc/foobar"

foobar_foomatic_file: "{{ foobar_config_path }}/foomatic.conf"

greeting: "Hello {% for host in groups['all'] %}{{ host }}, {% endfor %} and everybody else!"

block_string: |
  This is just a convenient YAML way for assigning multi-line strings to a variable,
  possibly with {{ 'splendid' if datacenter_location == 'UK' else 'awesome' }} magic
  embedded in it...

[Javeria Khan]

Right thanks guys. And what about using a condition that checks if my_dict contains a entry with name == name2 ? Its not a loop, just a conditional for file include so I need a one liner.