Python 检查 ansible 上 Jinja2 模板中的字典中是否存在键
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Check if key exists in a dict in Jinja2 template on ansible
提问by Alex
I have a host_var in ansible with dict with all interfaces:
我在 ansible 中有一个带有所有接口的 dict 的 host_var：
---
interfaces:
vlan0:
ip: 127.0.0.1
mask: 255.255.255.0
state: true
vlan2:
ip: 127.0.1.1
mask: 255.255.255.0
state: true
And I want to check if dict has a key vlan1if ok put to template value vlan1.ipelse put vlan2.ip.
我想检查 dict 是否有一个键vlan1如果可以放入模板值vlan1.ip否则放入vlan2.ip。
{% if interfaces.vlan1 %}
# and also I try {% if 'vlan1' in interfaces %}
{{ interfaces.vlan1.ip }};
{% else %}
{{ interfaces.vlan2.ip|default("127.0.0.1") }};
{% endif %};
But i have an error:
但我有一个错误：
fatal: [127.0.0.1] => {'msg': "AnsibleUndefinedVariable: One or more undefined variables: 'dict object' has no attribute 'vlan1'", 'failed': True}
I foundthat it have to be work in Jinja2 but it seems to doesn't work in ansible. Maybe someone have another way for solving this problem? When I define vlan1it works fine. Ansible version 1.9.2
我发现它必须在 Jinja2 中工作，但它似乎在 ansible 中不起作用。也许有人有另一种方法来解决这个问题？当我定义vlan1 时它工作正常。Ansible 版本 1.9.2
I was trying to reproduce it in python and have no error if my dictionary have not key vlan1. thanks to @GUIDO
我试图在 python 中重现它，如果我的字典没有键vlan1没有错误。感谢@GUIDO
>>> from jinja2 import Template
>>> b = Template("""
... {% if interfaces.vlan1 %}
... {{ interfaces.vlan1.ip }}
... {% else %}
... {{ interfaces.vlan2.ip|default("127.0.3.1") }}
... {% endif %}""")
>>> b.render(interfaces={'vlan3':{'ip':'127.0.1.1'},'vlan2':{'ip':'127.0.2.1'}})
u'\n\n127.0.2.1\n'
>>> b.render(interfaces={'vlan1':{'ip':'127.0.1.1'},'vlan2':{'ip':'127.0.2.1'}})
u'\n\n127.0.1.1\n'
采纳答案by Alex
The answer is simple and it showed on ansible error message. First of all I need to check if var is defined.
答案很简单，它显示在 ansible 错误消息中。首先，我需要检查是否定义了 var。
{% if interfaces.vlan1 is defined %}
{{ interfaces.vlan1.ip }}
{% else %}
{{ interfaces.vlan2.ip|default("127.0.3.1") }}
{% endif %}
This combination works well.
这种组合效果很好。
回答by larsks
The best way to check if a key exists in a dictionary (in any Jinja2 context, not just with Ansible) is to use the inoperator, e.g.:
检查字典中是否存在键的最佳方法（在任何 Jinja2 上下文中，而不仅仅是在 Ansible 中）是使用in运算符，例如：
{% if 'vlan1' in interfaces %}
{{ interfaces.vlan1.ip |default(interfaces.vlan2.ip) }};
{% endif %}
