How to count the number of elements in an array in Ansible?
Emily Wong 
An array is generated in Ansible from shell command output, it is similar to below:
foo: [value0, value1, value2, value3]Now depending on output of the shell command, the number of elements of foo may vary.
I then generate a jinja2 template to show :
foo[0] will return value0
foo[1] will return value1
...How would I determine how many elements are stored in foo?
2 Answers
Number_of_elements: "{{ foo|length }}"Just to expand on Vladimir Botka's response, you really need to check to make sure your item is a list (or a dictionary) first! It's very easy to make a mistake around type checking, as this can be a very easy slip-up to make.
Just to prove this, here's a sample playbook:
---
- hosts: localhost gather_facts: false vars: a_string: abcd1234 a_list: ['a', 'short', 'list'] a_dict: {'a': 'dictionary', 'with': 'values'} tasks: - debug: msg: | [ "a_string length: {{ a_string | length }}", "a_list length: {{ a_list | length }}", "a_dict length: {{ a_dict | length }}" ]And the result:
PLAY [localhost] ******************************************************************************************************************************
TASK [debug] **********************************************************************************************************************************
ok: [localhost] => { "msg": [ "a_string length: 8", "a_list length: 3", "a_dict length: 2" ]
}
PLAY RECAP ************************************************************************************************************************************
localhost : ok=1 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0 So, how can we confirm that this is, in fact, a list before we want to check the number of elements?
Like this:
{% if my_value is string %} 1
{% elif my_value is iterable %} {{ my_value | length }}
{% endif %}We have to check if it's a string first as strings are also iterable, whereas dictionaries (mapping) and lists (sequences) are not strings. Integers and Floats don't have a "length" property, so perhaps you should check for that first too (using if my_value is number)?
