Here is how you can create an empty dictionary using vars, a dictionary that contain no keys and no values.

---
- hosts: localhost
  vars:
    food: {}
  tasks:
  - debug: 
      var: food
...

Which should return the following.

ok: [localhost] => {
    "food": {}
}

Here is how you could create a dictionary that contains some key value pairs.

---
- hosts: localhost
  vars:
    food: 
      - { key: 'fruit', value: 'apple' }
      - { key: 'fruit', value: 'banana' }
      - { key: 'veggy', value: 'onion' }
      - { key: 'veggy', value: 'pepper' }
  tasks:
  - debug: 
      var: food
...

Or like this.

---
- hosts: localhost
  vars:
    food:
      - key: fruit
        value: apple
      - key: fruit
        value: banana
      - key: veggy
        value: onion
      - key: veggy
        value: pepper
  tasks:
  - debug: 
      var: food
...

Which should return the following.

ok: [localhost] => {
    "food": [
        {
            "key": "fruit",
            "value": "apple"
        },
        {
            "key": "fruit",
            "value": "banana"
        },
        {
            "key": "veggy",
            "value": "onion"
        },
        {
            "key": "veggy",
            "value": "pepper"
        }
    ]
}

And here is how you could create a dictionary that contains a list of values.

---
- hosts: localhost
  tasks:
  - set_fact:
      dictionary: { list: [ 'foo', 'bar' ] }

  - debug:
      var: dictionary
...

Looping through a dictionary 

The following parameters can be used to loop through each item in a dictionary.

• loop (preferred)
• with_items
• with_list

In this example, the loop parameter is used to loop over the food dictionary.

- name: "loop through the 'food' hash"
  debug: 
    msg: "{{ item }}"
  loop:
    - { key: 'fruit', value: 'apple' }
    - { key: 'fruit', value: 'banana' }
    - { key: 'veggy', value: 'onion' }
    - { key: 'veggy', value: 'pepper' }

Which should return the following. Note that some or all of the output can be suppressed or limited using the no_log or loop_control parameters.

TASK [loop through the 'food' hash] 
ok: [server1.example.com] => (item={'key': 'fruit', 'value': 'apple'}) => {
    "msg": {
        "key": "fruit",
        "value": "apple"
    }
}
ok: [server1.example.com] => (item={'key': 'fruit', 'value': 'banana'}) => {
    "msg": {
        "key": "fruit",
        "value": "banana"
    }
}
ok: [server1.example.com] => (item={'key': 'veggy', 'value': 'onion'}) => {
    "msg": {
        "key": "veggy",
        "value": "onion"
    }
}
ok: [server1.example.com] => (item={'key': 'veggy', 'value': 'pepper'}) => {
    "msg": {
        "key": "veggy",
        "value": "pepper"
    }
}