Ansible pick dictionary out of a list of dictionaries

问题

Variable mule_runtimes has a list of dictionaries:

- id: N-Newton
  version: 4.3.0
- id: N-Galileo
  version: 3.9.0-hf4
- id: N-Einstein
  version: 3.8.5-hf4

I want the dictionary with id = N-Einstein.

I have tried using this:

- debug:
    msg: "{{ mule_runtimes | selectattr('id', 'equalto', 'N-Einstein') | to_json }}"

And got error: Unexpected templating type error occurred on ({{ mule_runtimes | selectattr('id', 'equalto', 'N-Einstein') | to_json }}): Object of type 'generator' is not JSON serializable. What's the correct way to pick a dictionary from a list?

回答1:

The first problem is that mule_runtimes | selectattr('id', 'equalto', 'N-Einstein') returns a generator. Think of it like d for d in mule_runtimes if d['id'] == 'N-Einstein' in Python. You'll need to convert it to something JSON serializable (like a list) before using the to_json filter.

The second problem is that it doesn't select only a single dictionary from the list. The predicate id == 'N-Einstein' could be true for multiple dictionaries. If you know it will only match one dictionary, you'll need to convert the list to a single dictionary.

Putting that all together:

{{ mule_runtimes | selectattr('id', 'equalto', 'N-Einstein') | list | last | to_json }}

回答2:

I suggest json_query:

- name: dictionaries                                                            
  vars:                                                                         
    mule_runtimes:                                                              
      - id: N-Newton                                                            
        version: 4.3.0                                                          
      - id: N-Galileo                                                           
        version: 3.9.0-hf4                                                      
      - id: N-Einstein                                                          
        version: 3.8.5-hf4                                                      
    json: "{{ mule_runtimes }}"                                                 
    query: "[?id=='{{ want }}'].version"                                        
    want: N-Einstein                                                            
  debug:                                                                        
    msg: "{{ json | json_query(query) }}"

Gives the output:

TASK [test : dictionaries] *****************************************************                                                                               
ok: [127.0.0.1] => {                                                            
    "msg": [                                                                    
        "3.8.5-hf4"                                                             
    ]                                                                           
} 

来源：https://stackoverflow.com/questions/62313989/ansible-pick-dictionary-out-of-a-list-of-dictionaries