Ansible: Remove item from dict

Ansible: Remove item from dict

In Ansible, working with dictionaries (or maps) often involves manipulating key-value pairs, including removing specific items (keys) from a dictionary. While Ansible doesn't have a built-in task to directly remove a key from a dictionary, you can use Jinja2 filters to achieve this behavior.

Here's how you can remove a key from a dictionary in Ansible:

Method 1: Use combine to Create a New Dictionary Without the Key

To remove a key from a dictionary, create a new dictionary by excluding the undesired key(s) using Jinja2's dict filter with items() method or conditional expressions.

--- - name: Remove a key from a dictionary hosts: all vars: my_dict: key1: "value1" key2: "value2" key3: "value3" tasks: - name: Create a new dictionary without a specific key set_fact: updated_dict: "{{ my_dict | dict2items | rejectattr('key', 'eq', 'key2') | items2dict }}" - name: Display the new dictionary debug: var: updated_dict 

Explanation

  • dict2items: Converts a dictionary to a list of key-value pairs (dict items).
  • rejectattr: Rejects dictionary items based on a condition. In this case, the key "key2" is rejected.
  • items2dict: Converts the list of dictionary items back into a dictionary.

By using this approach, you create a new dictionary that omits the undesired key, achieving the desired effect of "removing" a key from a dictionary.

Method 2: Use a Loop to Create a New Dictionary Without the Key

If you need more flexibility, such as removing multiple keys or performing additional operations, you can loop through the dictionary items to create a new dictionary without specific keys.

--- - name: Remove multiple keys from a dictionary hosts: all vars: my_dict: key1: "value1" key2: "value2" key3: "value3" key4: "value4" tasks: - name: Remove multiple keys set_fact: updated_dict: "{{ {} }}" - name: Add keys to the new dictionary, excluding unwanted keys set_fact: updated_dict: "{{ updated_dict | combine({item.key: item.value}) }}" loop: "{{ my_dict | dict2items | rejectattr('key', 'in', ['key2', 'key4']) }}" - name: Display the updated dictionary debug: var: updated_dict 

Explanation

  • Creating an Empty Dictionary: Initializes an empty dictionary to build the new result.
  • Looping through Dictionary Items: Iterates over the items from the original dictionary, adding only those items that do not match the unwanted keys.
  • combine: Combines the new dictionary with each key-value pair from the loop, excluding the specified keys.

With these methods, you can effectively remove key-value pairs from dictionaries in Ansible, allowing for more dynamic manipulation and restructuring of data.

Examples

  1. Ansible: Remove Key from Dictionary

    • Use the set_fact module to remove a key from a dictionary.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 tasks: - name: Remove key from dictionary set_fact: my_dict: "{{ my_dict | dict2items | rejectattr('key', 'eq', 'key1') | items2dict }}" 
  2. Ansible: Filter Dictionary by Excluding Key

    • Use rejectattr to create a new dictionary without a specific key.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 tasks: - name: Exclude key from dictionary set_fact: filtered_dict: "{{ my_dict | dict2items | rejectattr('key', 'eq', 'key2') | items2dict }}" 
  3. Ansible: Remove Multiple Keys from Dictionary

    • Remove multiple keys from a dictionary by using a list of keys to exclude.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 key3: value3 keys_to_remove: - key1 - key2 tasks: - name: Remove multiple keys from dictionary set_fact: my_dict: "{{ my_dict | dict2items | rejectattr('key', 'in', keys_to_remove) | items2dict }}" 
  4. Ansible: Conditionally Remove Key from Dictionary

    • Conditionally remove a key from a dictionary based on a condition.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 remove_key1: true tasks: - name: Conditionally remove key1 from dictionary set_fact: my_dict: "{{ my_dict | dict2items | (remove_key1 | ternary(rejectattr('key', 'eq', 'key1'), identity)) | items2dict }}" 
  5. Ansible: Use Loop to Remove Specific Keys

    • Loop through a list of keys to remove them from a dictionary.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 key3: value3 keys_to_remove: - key2 - key3 tasks: - name: Remove keys using loop set_fact: my_dict: "{{ my_dict }}" with_items: - "{{ keys_to_remove }}" loop_control: label: "{{ item }}" run_once: true when: "item in my_dict" - name: Delete key from dictionary set_fact: my_dict: "{{ my_dict | dict2items | rejectattr('key', 'eq', item) | items2dict }}" 
  6. Ansible: Remove Key from Dictionary if Exists

    • Check if a key exists before attempting to remove it from a dictionary.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 tasks: - name: Check if key1 exists before removing set_fact: my_dict: "{{ my_dict | dict2items | rejectattr('key', 'eq', 'key1') | items2dict }}" when: "'key1' in my_dict" 
  7. Ansible: Clear Dictionary

    • Remove all keys from a dictionary to clear it.
    - hosts: localhost tasks: - name: Clear dictionary set_fact: my_dict: {} 
  8. Ansible: Retain Specific Keys in Dictionary

    • Use selectattr to keep only specific keys in a dictionary.
    - hosts: localhost vars: my_dict: key1: value1 key2: value2 key3: value3 keys_to_keep: - key1 - key3 tasks: - name: Keep only specific keys in dictionary set_fact: retained_dict: "{{ my_dict | dict2items | selectattr('key', 'in', keys_to_keep) | items2dict }}" 
  9. Ansible: Remove Nested Dictionary Item

    • Access nested dictionary keys to remove a specific item.
    - hosts: localhost vars: my_dict: nested: key1: value1 key2: value2 tasks: - name: Remove nested key2 set_fact: my_dict: "{{ my_dict }}" - name: Modify nested dictionary set_fact: my_dict: "{{ my_dict.update({ 'nested': my_dict['nested'] | dict2items | rejectattr('key', 'eq', 'key2') | items2dict }) }}" 

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