您应该使用 default 过滤器，带有 omit 变量.

You should use the default filter with the omit variable for that.

- docker_container:
    name: myapplication
    ports: "{{ port|default(omit) if port is not defined else [port] }}"

请注意，您要使用这种确切的语法，而不是像

Mind that you want to use this exact syntax and not the array notation like

- docker_container:
    name: myapplication
    ports:
      - "{{ port|default(omit) }}"

否则你将在属性 ports 中得到一个数组，但仍然会有一些奇怪的值，比如

Otherwise you will end up with an array in the attribute ports, still, that would have some odd value like

"__omit_place_holder__ad3616ee8afa39aa187d7fc6ac7ad36f3e7691c0"