Django模板如何使用变量查找字典值

问题:Django模板如何使用变量查找字典值

mydict = {"key1":"value1", "key2":"value2"}

查找在Django模板字典值的常规方法是{{ mydict.key1 }}{{ mydict.key2 }}。如果键是循环变量怎么办?即:

{% for item in list %} # where item has an attribute NAME
  {{ mydict.item.NAME }} # I want to look up mydict[item.NAME]
{% endfor %}

mydict.item.NAME失败。如何解决?

mydict = {"key1":"value1", "key2":"value2"}

The regular way to lookup a dictionary value in a Django template is {{ mydict.key1 }}, {{ mydict.key2 }}. What if the key is a loop variable? ie:

{% for item in list %} # where item has an attribute NAME
  {{ mydict.item.NAME }} # I want to look up mydict[item.NAME]
{% endfor %}

mydict.item.NAME fails. How to fix this?


回答 0

编写自定义模板过滤器:

from django.template.defaulttags import register
...
@register.filter
def get_item(dictionary, key):
    return dictionary.get(key)

(我.get这样使用,如果不存在该键,则不返回任何键。如果执行dictionary[key]此操作,则将引发一个KeyErrorthen。)

用法:

{{ mydict|get_item:item.NAME }}

Write a custom template filter:

from django.template.defaulttags import register
...
@register.filter
def get_item(dictionary, key):
    return dictionary.get(key)

(I use .get so that if the key is absent, it returns none. If you do dictionary[key] it will raise a KeyError then.)

usage:

{{ mydict|get_item:item.NAME }}

回答 1

从循环中的字典中获取键和值:

{% for key, value in mydict.items %}
    {{ value }}
{% endfor %}

我发现这更容易阅读,并且不需要特殊的编码。无论如何,我通常都需要循环内的键和值。

Fetch both the key and the value from the dictionary in the loop:

{% for key, value in mydict.items %}
    {{ value }}
{% endfor %}

I find this easier to read and it avoids the need for special coding. I usually need the key and the value inside the loop anyway.


回答 2

默认情况下不能。点是属性查找/键查找/切片的分隔符/触发器。

点在模板渲染中具有特殊含义。变量名称中的点表示查找。具体来说,当模板系统遇到变量名称中的点时,它将按以下顺序尝试以下查找:

  • 字典查找。示例:foo [“ bar”]
  • 属性查询。示例:foo.bar
  • 列表索引查找。示例:foo [bar]

但是您可以创建一个过滤器,以便您传递参数:

https://docs.djangoproject.com/zh-CN/dev/howto/custom-template-tags/#writing-custom-template-filters

@register.filter(name='lookup')
def lookup(value, arg):
    return value[arg]

{{ mydict|lookup:item.name }}

You can’t by default. The dot is the separator / trigger for attribute lookup / key lookup / slice.

Dots have a special meaning in template rendering. A dot in a variable name signifies a lookup. Specifically, when the template system encounters a dot in a variable name, it tries the following lookups, in this order:

  • Dictionary lookup. Example: foo[“bar”]
  • Attribute lookup. Example: foo.bar
  • List-index lookup. Example: foo[bar]

But you can make a filter which lets you pass in an argument:

https://docs.djangoproject.com/en/dev/howto/custom-template-tags/#writing-custom-template-filters

@register.filter(name='lookup')
def lookup(value, arg):
    return value[arg]

{{ mydict|lookup:item.name }}

回答 3

对我来说template_filters.py,用下面的内容在我的应用程序中创建一个名为python的文件就可以了

# coding=utf-8
from django.template.base import Library

register = Library()


@register.filter
def get_item(dictionary, key):
    return dictionary.get(key)

用法就像culebrón所说的:

{{ mydict|get_item:item.NAME }}

For me creating a python file named template_filters.py in my App with below content did the job

# coding=utf-8
from django.template.base import Library

register = Library()


@register.filter
def get_item(dictionary, key):
    return dictionary.get(key)

usage is like what culebrón said :

{{ mydict|get_item:item.NAME }}

回答 4

我也有类似的情况。但是我使用了不同的解决方案。

在我的模型中,我创建一个执行字典查找的属性。然后在模板中使用该属性。

在我的模型中:-

@property
def state_(self):
    """ Return the text of the state rather than an integer """
    return self.STATE[self.state]

在我的模板中:-

The state is: {{ item.state_ }}

I had a similar situation. However I used a different solution.

In my model I create a property that does the dictionary lookup. In the template I then use the property.

In my model: –

@property
def state_(self):
    """ Return the text of the state rather than an integer """
    return self.STATE[self.state]

In my template: –

The state is: {{ item.state_ }}

回答 5

因为我不能评论,让我做这一个答案的形式:
建立在culebrón的答案虞姬“富田”富田的答案,传递给函数的字典是一个字符串的形式,因此,也许使用AST。 literal_eval,首先将字符串转换为字典,如本例所示

通过此编辑,代码应如下所示:

@register.filter(name='lookup')
def lookup(value, arg):
    dictionary = ast.literal_eval(value)
    return value.get(arg)

{{ mydict|lookup:item.name }}

Since I can’t comment, let me do this in the form of an answer:
to build on culebrón’s answer or Yuji ‘Tomita’ Tomita’s answer, the dictionary passed into the function is in the form of a string, so perhaps use ast.literal_eval to convert the string to a dictionary first, like in this example.

With this edit, the code should look like this:

# code for custom template tag
@register.filter(name='lookup')
def lookup(value, arg):
    value_dict = ast.literal_eval(value)
    return value_dict.get(arg)

<!--template tag (in the template)-->
{{ mydict|lookup:item.name }}

回答 6

环境:Django 2.2

  1. 示例代码:


    from django.template.defaulttags import register

    @register.filter(name='lookup')
    def lookup(value, arg):
        return value.get(arg)

我将此代码放在名为Portfoliomgr的项目文件夹中的一个名为template_filters.py的文件中

  1. 无论您将过滤器代码放在何处,都要确保该文件夹中有__init__.py

  2. 将该文件添加到projectfolder / settings.py文件中模板部分的库部分。对我来说,它是Portfoliomgr / settings.py



    TEMPLATES = [
        {
            'BACKEND': 'django.template.backends.django.DjangoTemplates',
            'DIRS': [os.path.join(BASE_DIR, 'templates')],
            'APP_DIRS': True,
            'OPTIONS': {
                'context_processors': [
                    'django.template.context_processors.debug',
                    'django.template.context_processors.request',
                    'django.contrib.auth.context_processors.auth',
                    'django.contrib.messages.context_processors.messages',
                ],
                'libraries':{
                    'template_filters': 'portfoliomgr.template_filters',
                }
            },
        },
    ]
  1. 在您的html代码中加载库

    
    {% load template_filters %}

Environment: Django 2.2

  1. Example code:


    from django.template.defaulttags import register

    @register.filter(name='lookup')
    def lookup(value, arg):
        return value.get(arg)

I put this code in a file named template_filters.py in my project folder named portfoliomgr

  1. No matter where you put your filter code, make sure you have __init__.py in that folder

  2. Add that file to libraries section in templates section in your projectfolder/settings.py file. For me, it is portfoliomgr/settings.py



    TEMPLATES = [
        {
            'BACKEND': 'django.template.backends.django.DjangoTemplates',
            'DIRS': [os.path.join(BASE_DIR, 'templates')],
            'APP_DIRS': True,
            'OPTIONS': {
                'context_processors': [
                    'django.template.context_processors.debug',
                    'django.template.context_processors.request',
                    'django.contrib.auth.context_processors.auth',
                    'django.contrib.messages.context_processors.messages',
                ],
                'libraries':{
                    'template_filters': 'portfoliomgr.template_filters',
                }
            },
        },
    ]

  1. In your html code load the library

    
    {% load template_filters %}
    

回答 7

环保:django 2.1.7

视图:

dict_objs[query_obj.id] = {'obj': query_obj, 'tag': str_tag}
return render(request, 'obj.html', {'dict_objs': dict_objs})

模板:

{% for obj_id,dict_obj in dict_objs.items %}
<td>{{ dict_obj.obj.obj_name }}</td>
<td style="display:none">{{ obj_id }}</td>
<td>{{ forloop.counter }}</td>
<td>{{ dict_obj.obj.update_timestamp|date:"Y-m-d H:i:s"}}</td>

env: django 2.1.7

view:

dict_objs[query_obj.id] = {'obj': query_obj, 'tag': str_tag}
return render(request, 'obj.html', {'dict_objs': dict_objs})

template:

{% for obj_id,dict_obj in dict_objs.items %}
<td>{{ dict_obj.obj.obj_name }}</td>
<td style="display:none">{{ obj_id }}</td>
<td>{{ forloop.counter }}</td>
<td>{{ dict_obj.obj.update_timestamp|date:"Y-m-d H:i:s"}}</td>