如何在ansible循环中跳过空值

我需要从 ansible 循环中的列表中跳过值 null。我正在使用 when 条件，仍然打印空值。下面是我的剧本：

 - hosts: localhost
   vars:
    show:
     - read
     - write
     - null
     - test
    val: []
   tasks:
   - name: Fact
     set_fact:
      val: "{{val+[item]}}"
     loop: "{{show}}"
     when: item != "null"

   - name: Print
     debug:
      msg: "{{val}}"

输出：

TASK [Print] ***
ok: [localhost] => {
    "msg": [
        "read",
        "write",
        null,
        "test"
    ]
}

请指教。

回答

when: item != None 

when: item is not none

when: item|string != 'None'

loop: "{{ show|reject('none')|list }}"