Ansible会自动翻转变量。

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英文:

Ansible automatically flips variable

问题

我最近遇到了Ansible的一个非常奇怪的行为，想知道为什么会发生这种情况。

我使用的是Ansible 2.7.7和Python 3.5.3。

具体来说，我有两个变量：

  1. GLOBAL_HIGHEST_PARAM: "{5,0}"
  2. LOCAL_HIGHEST_PARAM: "{5,0}"

并且在使用LOCAL_HIGHEST_PARAM时，例如像这样：

  1. - name: 设置最高分参数 {{ LOCAL_HIGHEST_PARAM }}
  2.   # ...

在运行时给我正确的输出：设置最高分参数 {5,0}

但是当我定义变量如下：

  1. GLOBAL_HIGHEST_PARAM: "{5,0}"
  2. LOCAL_HIGHEST_PARAM: "{{ GLOBAL_HIGHEST_PARAM }}"

我得到了不正确的输出：设置最高分参数 {0,5}

为什么会发生这种情况？

英文:

I recently came across a very strange behavior of Ansible and would like to know why this is happening.

I'm using Ansible 2.7.7 with python 3.5.3.

So to the point.
I have two variables:

  1. GLOBAL_HIGHEST_PARAM: "{5,0}"
  2. LOCAL_HIGHEST_PARAM: "{5,0}"

And using LOCAL_HIGHEST_PARAM for example like this:

  1. - name: Setting up highest score param {{ LOCAL_HIGHEST_PARAM }}
  2.   # ...

Which gives me the correct output during run: Setting up highest score param {5,0}

But when I define variables such as:

  1. GLOBAL_HIGHEST_PARAM: "{5,0}"
  2. LOCAL_HIGHEST_PARAM: "{{ GLOBAL_HIGHEST_PARAM }}"

I get the incorrect output: Setting up highest score param {0,5}

Why is this happening?

答案1

得分: 2

  1. 这是因为`{5,0}`实际上是一个[Python集合](https://docs.python.org/3.11/library/stdtypes.html#set-types-set-frozenset)，你可以在调试变量时看到：
  3. ```yaml
  4. - debug:
  5.     msg: "{{ GLOBAL_HIGHEST_PARAM }}"
  6.   vars:
  7.     GLOBAL_HIGHEST_PARAM: "{5,0}"

会产生：

  1. ok: [localhost] => 
  2.   msg: !!set
  3.     0: null
  4.     5: null

由于5和0是集合的键，所以集合会按键排序。

你可以使用Jinja的string过滤器强制将其表示为字符串。

任务：

  1. - debug:
  2.     msg: "{{ LOCAL_HIGHEST_PARAM }}"
  3.   vars:
  4.     GLOBAL_HIGHEST_PARAM: "{5,0}"
  5.     LOCAL_HIGHEST_PARAM: "{{ GLOBAL_HIGHEST_PARAM | string }}"

会得到你期望的结果：

  1. ok: [localhost] => 
  2.   msg: '{5,0}'

请注意，在任务名称中可以正常工作，因为任务名称只能是字符串，所以它会隐式转换为字符串，在其他情况下可能不会，除非使用显式的string过滤器。

  2. <details>
  3. <summary>英文:</summary>
  5. This happens because `{5,0}` is actually a [Python set](https://docs.python.org/3.11/library/stdtypes.html#set-types-set-frozenset), which you can actually see debugging the variable:
  7. ```yaml
  8. - debug:
  9.     msg: &quot;{{ GLOBAL_HIGHEST_PARAM }}&quot;
  10.   vars:
  11.     GLOBAL_HIGHEST_PARAM: &quot;{5,0}&quot;

Would yield:

  1. ok: [localhost] =&gt; 
  2.   msg: !!set
  3.     0: null
  4.     5: null

And since 5 and 0 are the keys of the set, the set get sorted by keys.

You can force it to be represented as a string, though, with the string filter of Jinja.

The task:

  1. - debug:
  2.     msg: &quot;{{ LOCAL_HIGHEST_PARAM }}&quot;
  3.   vars:
  4.     GLOBAL_HIGHEST_PARAM: &quot;{5,0}&quot;
  5.     LOCAL_HIGHEST_PARAM: &quot;{{ GLOBAL_HIGHEST_PARAM | string }}&quot;

Will give you the expected

  1. ok: [localhost] =&gt; 
  2.   msg: &#39;{5,0}&#39;

Note that it does work in a task name because tasks names can only be string, so it is implicitly casted as a string, while it might not be, in other cases, without an explicit string filter.

huangapple
  • 本文由 发表于 2023年7月17日 18:40:56
  • 转载请务必保留本文链接：https://go.coder-hub.com/76703659.html
  • ansible
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