This behavior of Jinja always confuses in Ansible

playbook.yml

- hosts: localhost
  gather_facts: no
  vars:
    thing:
  tasks:
    - name: Print double quotes
      debug:
        msg: "{{ thing | default('empty string') }}"

    - name: Print empty string
      debug:
        msg: "{{ thing | default('empty string', True) }}"

playbook_output.txt

# ansible-playbook test.yml
PLAY [localhost] *******************************************************************

TASK [Print double quotes] *********************************************************
ok: [localhost] => {
    "msg": ""
}

TASK [Print empty string] **********************************************************
ok: [localhost] => {
    "msg": "empty string"
}

PLAY RECAP *************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0

python.py

>>> foo = ""
>>> if foo:
...   print('oi')
... 
>>>