Accessing values of nested dictionaries - variables

Question

I'm working some separate tasks for automating VM deployments through tower.
Basically I just need a quick run down on how to gather/use the various properties of a registered return from a task.
I've got this.
tasks:
- name: Gather disk info from virtual machine using name
vmware_guest_disk_info:
hostname: "{{ vcenter }}"
username: "{{ username }}"
password: "{{ esxipassword }}"
datacenter: "{{ datacenter }}"
name: "{{ fqdn }}"
register: disk_info
- debug:
var: disk_info
This spits out the information I want. But, for the life of me I can't figure out how to select a single property. can someone tell me how to do that (particularly for the backing_filename) property?
I mean in powershell it would just be disk_info.backing_filename or something like backing = $disk_info | select -expandproperty backing_filename. Just looking for something like the equivalent of that.
Snip of output
{
"disk_info": {
"guest_disk_info": {
"0": {
"key": 2000,
"label": "Hard disk 1",
"summary": "104,857,600 KB",
"backing_filename": "[datastorex] vmname/vmname.vmdk",

Answer 1

To be fair, this one is not as simple as it looks, because your dictionary has a key being a string 0, but, would you be doing disk_info.guest_disk_info.0.backing_filename you would try to access an element 0, so a list, and not a dictionary key '0'.
Here would be an example playbook solving your issue:
- hosts: all
gather_facts: yes
tasks:
- debug:
var: disk_info.guest_disk_info['0'].backing_filename
vars:
disk_info:
guest_disk_info:
'0':
key: 2000
label: Hard disk 1
summary: 104,857,600 KB
backing_filename: "[datastorex] vmname/vmname.vmdk"
That gives:
{
"disk_info.guest_disk_info['0'].backing_filename": "[datastorex] vmname/vmname.vmdk"
}
While this works also, you would see that the YAML is representing a totally different structure, also including a list, and not only multiple nested dictionaries:
- hosts: all
gather_facts: yes
tasks:
- debug:
var: disk_info.guest_disk_info.0.backing_filename
vars:
disk_info:
guest_disk_info:
- key: 2000
label: Hard disk 1
summary: 104,857,600 KB
backing_filename: "[datastorex] vmname/vmname.vmdk"
To give you an equivalent in JSON, since you seems to have issue understanding the YAML constructions, your output is
{
"disk_info": {
"guest_disk_info": {
"0": {
"backing_filename": "[datastorex] vmname/vmname.vmdk"
}
}
}
}
That would be accessible via disk_info.guest_disk_info['0'].backing_filename.
While
{
"disk_info": {
"guest_disk_info": [
{
"backing_filename": "[datastorex] vmname/vmname.vmdk"
}
]
}
}
Would be accessible via disk_info.guest_disk_info.0.backing_filename