Flatten nested dictionary to key/value pairs with Ansible - dictionary

Question

---
- hosts: localhost
vars:
mydict:
key1: val1
key2: val2
key3:
subkey1: subval1
subkey2: subval2
tasks:
- debug:
msg: "{{ TODO }}"
How would I make the above debug message print out all key/value pairs from the nested dictionary? Assume the depth is unknown. I would expect the output to be something like:
{
"key1": "val1",
"key2": "val2",
"subkey1": "subval1"
"subkey2": "subval2"
}

Answer 1

Write a filter plugin and use pandas.json_normalize, e.g.
shell> cat filter_plugins/dict_normalize.py
from pandas.io.json import json_normalize
def dict_normalize(d):
df = json_normalize(d)
l = [df.columns.values.tolist()] + df.values.tolist()
return(l)
class FilterModule(object):
def filters(self):
return {
'dict_normalize': dict_normalize,
}
The filter returns lists of keys and values
- set_fact:
mlist: "{{ mydict|dict_normalize }}"
gives
mlist:
- - key1
- key2
- key3.subkey1
- key3.subkey2
- - val1
- val2
- subval1
- subval2
Create a dictionary, e.g.
- debug:
msg: "{{ dict(mlist.0|zip(mlist.1)) }}"
gives
msg:
key1: val1
key2: val2
key3.subkey1: subval1
key3.subkey2: subval2
If the subkeys are unique remove the path
- debug:
msg: "{{ dict(_keys|zip(mlist.1)) }}"
vars:
_regex: '^(.*)\.(.*)$'
_replace: '\2'
_keys: "{{ mlist.0|map('regex_replace', _regex, _replace)|list }}"
gives
msg:
key1: val1
key2: val2
subkey1: subval1
subkey2: subval2
Notes
Install the package, e.g. python3-pandas
The filter might be extended to support all parameters of json_normalize
The greedy regex works also in nested dictionaries
Q: "Turn the key3.subkey1 to get the original dictionary."
A: Use json_query. For example, given the dictionary created in the first step
- set_fact:
mydict_flat: "{{ dict(mlist.0|zip(mlist.1)) }}"
mydict_flat:
key1: val1
key2: val2
key3.subkey1: subval1
key3.subkey2: subval2
iterate the keys and retrieve the values from mydict
- debug:
msg: "{{ mydict|json_query(item) }}"
loop: "{{ mydict_flat|list }}"
gives
msg: val1
msg: val2
msg: subval1
msg: subval2