Berry Langerak Berry Langerak - 4 months ago 6x
Python Question

merging dictionaries in ansible

I'm currently building a role for installing PHP using ansible, and I'm having some difficulty merging dictionaries. I've tried several ways to do so, but I can't get it to work like I want it to:

# A vars file:
key = value

my_key = my_value

# In a playbook, I create a task to attempt merging the
# two dictionaries (which doesn't work):

- debug: msg="{{ item.key }} = {{ item.value }}"
with_dict: my_default_values + my_values

# I have also tried:

- debug: msg="{{ item.key }} = {{ item.value }}"
with_dict: my_default_values|union(my_values)

# I have /some/ success with using j2's update,
# but you can't use j2 syntax in "with_dict", it appears.
# This works:

- debug: msg="{{ my_default_values.update(my_values) }}"

# But this doesn't:

- debug: msg="{{ item.key }} = {{ item.value }}"
with_dict: my_default_values.update(my_values)

Is there a way to merge two dictionaries, so I can use it with "with_dict"?


If you want hash merging I would turn the hash merging feature on in ansible. In your ansible config file turn hash merging on.

With hash_behaviour=merge you can have two var files with the same variable name:


  key: value


  my_key: my_value

In order for the two vars to be merged you will need to include both var files:

ansible-playbook some-play.yml ... -e@defaults.yml  -e@overrides.yml

And you will end up with this:

TASK: [debug var=values] ********************************************************
ok: [localhost] => {
    "values": {
        "key": value,
        "my_key": my_value

Calling update on a variable can be done in Jinja but in general it will be messy, I wouldn't do it outside of your templates and even then try to avoid it altogether.