Jinja2 无法检索字典中键的值

Question

I am trying to extract the value of volume_snapshot_schedules but I can't seem to make it right.

This key is a part of a dictionary where I am able to extract the values of its other keys but not this one.

This is the dictionary as printed by ansible (but simplified):

policy: [{
'comment': 'Default policy with hourly, daily & weekly schedules.', 
'enabled': 'true', 
'policy': 'default', 
'policy_owner': 'cluster-admin', 
'snapshot_policy_schedules': {
'snapshot_schedule_info': 
[
{'count': '6', 'prefix': 'hourly', 'schedule': 'hourly', 'snapmirror_label': '-'}, 
{'count': '2', 'prefix': 'daily', 'schedule': 'daily', 'snapmirror_label': 'daily'}, 
{'count': '2', 'prefix': 'weekly', 'schedule': 'weekly', 'snapmirror_label': 'weekly'}
]}
}]

If I print the output of {{ policy.value }} , the following is printed:

{
'comment': 'Default policy with hourly, daily & weekly schedules.', 
'enabled': 'true', 
'policy': 'default', 
'policy_owner': 'cluster-admin', 
'snapshot_policy_schedules': {
'snapshot_schedule_info': 
{'count': '6', 'prefix': 'hourly', 'schedule': 'hourly', 'snapmirror_label': '-'}, 
{'count': '2', 'prefix': 'daily', 'schedule': 'daily', 'snapmirror_label': 'daily'}, 
{'count': '2', 'prefix': 'weekly', 'schedule': 'weekly', 'snapmirror_label': 'weekly'}
}

If I print the value of {{ policy.value.comment }} or {{ policy.value.policy }} , I get the appropriate value as expected.

However, when I print the value of {{ policy.value.snapshot_policy_schedules }} , it fails with error:

fatal: [localhost]: FAILED! => {"changed": false, "msg": "AnsibleUndefinedVariable: 'dict object' has no attribute 'snapshot_policy_schedules'"}

I then tried to convert it to a list {{ policy.value.snapshot_policy_schedules|list }} but that showed the same error message.

Edit: When I try {{ policy.value.snapshot_policy_schedules[0] }} , the following error is shown:

fatal: [localhost]: FAILED! => {"changed": false, "msg": "AnsibleUndefinedVariable: dict object has no element 0"}

Answer 1

I think you have to access the position of the list like that:

{{ policy.value.snapshot_policy_schedules[0] }}

because its an array and it can have multiple lists, another option that I don't know is that you have to call it like that:

{ policy.value.snapshot_policy_schedules.snapshot_schedule_info[0]}}

The reason you are getting correct values on the policy is that it's a single value and not a list/array, so you don't need to access any position because it only have 1 value.

Answer 2

I dont think you can access the values with {{ policy.value.comment }} or {{ policy.value.policy }} as they are in inline list.
There are multiple ways to get the values inside list. I think the easy one is json_query filter
For example if I recreate your scenario, to get the values for 'comment' and 'snapshot_policy_schedules', use json_query as below
- hosts: localhost
  gather_facts: no
  vars: 
    policy: [{
      'comment': 'Default policy with hourly, daily & weekly schedules.', 
      'enabled': 'true', 
      'policy': 'default', 
      'policy_owner': 'cluster-admin', 
      'snapshot_policy_schedules': {
      'snapshot_schedule_info': 
      [
      {'count': '6', 'prefix': 'hourly', 'schedule': 'hourly', 'snapmirror_label': '-'}, 
      {'count': '2', 'prefix': 'daily', 'schedule': 'daily', 'snapmirror_label': 'daily'}, 
      {'count': '2', 'prefix': 'weekly', 'schedule': 'weekly', 'snapmirror_label': 'weekly'}
      ]}
      }]
  tasks:
  - debug: 
      var: policy|json_query('[*].comment')
  - debug: 
      var: policy|json_query('[*].snapshot_policy_schedules')
------------------------------------------------------------------------------------------------------------------------------
*OUTPUT
TASK [debug] ************************************************************************************************************************************************************
ok: [localhost] => {
    "policy|json_query('[*].comment')": [
        "Default policy with hourly, daily & weekly schedules."
    ]
}
TASK [debug] ************************************************************************************************************************************************************
ok: [localhost] => {
    "policy|json_query('[*].snapshot_policy_schedules')": [
        {
            "snapshot_schedule_info": [
                {
                    "count": "6",
                    "prefix": "hourly",
                    "schedule": "hourly",
                    "snapmirror_label": "-"
                },
                {
                    "count": "2",
                    "prefix": "daily",
                    "schedule": "daily",
                    "snapmirror_label": "daily"
                },
                {
                    "count": "2",
                    "prefix": "weekly",
                    "schedule": "weekly",
                    "snapmirror_label": "weekly"
                }
            ]
        }
    ]
}*