filtering out attributes

[Justin DynamicD]

First I apologize if this was covered elsewhere, but nothing seemed to match my scenario... at least not in a way I could recreate.

I have a role that builds a list of dictionaries.  I've found it fairly easy to extend this list, add attributes to individual items, etc, but I'm having a real problem "reducing" the output or creating a simplified dictionary from the complex one.

The scenario:

Assume I have a list that looks something like this:

drives:
 - volume: 0
   size_kb: 102400
   name: drive1
   datastore: alpha
 - volume: 1
   size_gb: 50
   name: drive2
   datastore: alpha

In this case, I discover with minor manipulation, I can drop {{ drives }} right into my vmware_guest module as long as I filter down to just the relevant attributes.  If I drop it in as-is, however, it fails because it doesn't know what some of the attributes are.  So I want to make it look something like this:

drives:
 - size_kb: 102400
   datastore: alpha
 - size_gb: 50
   datastore: alpha

I've tried using selectattr() and rejectattr(), but those seem to accept/reject the entire dictionary based on an attribute.  I'm hoping to simply filter out irrelevant attributes instead.  I tried just making a new list but then had issues with dealing with the "size_*" attributes as one is kb and the other is gb.  Basically I would love to have some kind of filter where I set a new fact and simply inject every attribute that is relevant.

- set_fact:
    new_disks: "{{ new_disks | default([]) + [ drives | selectonly('datastore','size_*') ] }}"
  loop: "{{ drives }}"
  loop_control:
    loop_var: loop_drives

Sadly, I've been coming up empty when it comes to "trimming" an object down.  Any ideas?

[James Cassell]

Look at the json_query filter. You can use it with JMESPath queries to extract what you need.

V/r,
James Cassell

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