Python 当key是一个变量时，如何从jinja中的字典中获取值？
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How to get values from dictionary in jinja when key is a variable?
提问by tytk
I'm trying to retrieve entries from a python dictionary in jinja2, but the problem is I don't know what key I want to access ahead of time - the key is stored in a variable called s.course. So my problem is I need to double-substitute this variable. I don't want to use a forloop because that will go through the dictionary way more than is necessary. Here's a workaround that I created, but it's possible that the s.coursevalues could change so obviously hard-coding them like this is bad. I want it to work essentially like this:
我正在尝试从 jinja2 中的 python 字典中检索条目，但问题是我不知道我想提前访问哪个键 - 键存储在一个名为s.course. 所以我的问题是我需要双重替换这个变量。我不想使用for循环，因为它会比必要的更多地通过字典方式。这是我创建的一种解决方法，但s.course值可能会发生变化，很明显，像这样对它们进行硬编码是不好的。我希望它基本上像这样工作：
{% if s.course == "p11" %}
{{course_codes.p11}}
{% elif s.course == "m12a" %}
{{course_codes.m12a}}
{% elif s.course == "m12b" %}
{{course_codes.m12b}}
{% endif %}
But I want it to look like this:
但我希望它看起来像这样：
{{course_codes.{{s.course}}}}
Thanks!
谢谢！
采纳答案by R. Max
You can use course_codes.get(s.course):
您可以使用course_codes.get(s.course)：
>>> import jinja2
>>> env = jinja2.Environment()
>>> t = env.from_string('{{ codes.get(mycode) }}')
>>> t.generate(codes={'a': '123'}, mycode='a').next()
u'123'
回答by onlyanegg
I'm using Jinja with Salt, and I've found that something like the following works well:
我正在将 Jinja 与 Salt 一起使用，我发现类似以下内容的效果很好：
{% for role in pillar.packages %}
{% for package in pillar['packages'][role] %}
install_{{ package }}:
pkg.installed:
- name: {{ package }}
{% endfor %}
{% endfor %}
That is, use the more verbose [ ]syntax and leave the quotes out when you need to use a variable.
也就是说，[ ]当您需要使用变量时，使用更详细的语法并省略引号。
回答by Mike Vella
There is no need to use the dot notation at all, you can do:
根本不需要使用点符号，你可以这样做：
"{{course_codes[s.course]}}"
