Django中的内置Tags

Dates

```
{% now "m/d/Y" %}
```

copyright {% now 'Y' as current_year %}

该tag也可以接受Django的date 变量，比如{% now 'SHORT_DATETIME_FORMAT' %}--> 09/05/2020 10:59 p.m.

{% now 'SHORT_DATE_FORMAT' %}-->09/05/2020

{% now 'DATE_FORMAT' %}-->Sept. 5, 2020

Forms

在

tag里使用{% csrf_token %}来防止跨域伪造请求攻击。

比较操作

{% if %}和{% elif %}和

与python 语法类似，不再赘述

{% first of %}是一个输出第一个不是空的变量的快捷用法。

#urls.py

{'var1':'','var2':1,'var3':2 }

{% firstof var1 var2 var3 %}

{% if %},{% elif %}的等效方法：

#firstof example

{% firstof var1 var2 var3 %}

#Equivalent of firstof example

{%if var1 %}

{{ var1|safe }}

{% elif var2 %}

{{ var2|safe }}

{% elif var3 %}

{{ var3|safe }}

{% endif %}

# Firstof example with a default value in case of no match( that is meaning all variables are empty)

{% firstof var1 var2 var3 'All vars are empty' %}

#Assign the firstof result to another variable

{% firstof var1 var2 var3 as resultof %}

{% if in %}, {% if not in %}
{% if is value %}, {% if is not value %}

{% if value| %}

比如：

#urls.py

{'drinklist':['coco','cola','milk'],'userdrink':'cola'}

{% if drinklist|random == userdrink %}

Yes it is

{% else %}

No

{% endif %}

需要注意的是，在{% if %}里不允许有“（）”，比如{% if drink in specials or drink== drink_of_day %}，不能写成 {% if (drink in specials) or (drink== drink_of_day) %}

Loops

{% for %},以及带{% empty %}的

#urls.py

{'drinks':['cola','coco','water']}

#html

{% for drink in drinks %}

{{ drink }}

{% endfor %}

#urls.py

{'drinks':[]}

{% for drink in drinks %}

{{ drink }}

{% empty %}

No drinks here

{% endfor %}

{% for %}也产生了一系列变量来对遍历过程进行控制：

Variable	Description
forloop.counter	The current iteration of the loop(1-indexed)
forloop.counter0	The current iteration of the loop(0-indexed)
forloop.revcounter	The number of the iterations from the end of the loop(1-indexed)
forloop.revcounter0	The number of the iterations from the end of the loop(0-indexed)
forloop.first	True,if it's the first time through the loop
forloop.last	True,if it's the last time through the loop

#urls.py

'drinks':['water','cola','coco','milk']

#html

{% for drink in drinks %}

<b>{{ drink }}</b><br>

forloop.counter-->{{ forloop.counter }}<br>

forloop.counter0-->{{ forloop.counter0 }}<br>

forloop.revcounter0-->{{ forloop.revcounter0 }}<br>

forloop.revcounter-->{{ forloop.revcounter }}<br>

forloop.first-->{{ forloop.first }}<br>

forloop.last-->{{ forloop.last }}<br>

{% empty %}

No drinks here

{% endfor %}

(1)一般放在{% for %}内，循环时，依次取其参数，如：

#urls.py

'drinks':['water','cola','coco','milk','coffee','wanglaoji']

#base.html

<!DOCTYPE html>

<head>

    <title>

        {% block title_block %}

        Base

        {% endblock %}

    </title>

    <style>

        .red {

            color:red;

        }

        .blue {

            color:blue;

        }

        .yellow {

            color:yellow;

        }

    </style>

</head>

<body>

    {% block body_block %}

    {% endblock %}

</body>

#rendered.html

{% extends 'banners/base.html' %}

{% block title_block %}

test

{% endblock %}

{% block body_block %}

<url>

    {% for drink in drinks %}

    <li class="{% cycle 'red' 'yellow' 'blue' %}">{{ drink }}</li>

</url>

{% endfor %}

{% endblock %}

drink在drinks中循环时，每次循环，依次取'red'，‘yellow','blue'，然后周而复始，如下：

{% cycle %} 的参数也可以是变量，如将上述urls.py和rendered.html换成如下，效果一样：

#urls.py

'drinks':['water','cola','coco','milk','coffee','wanglaoji'],'r':'red','b':'blue','y':'yellow'

#rendered.html

{% extends 'banners/base.html' %}

{% block title_block %}

test

{% endblock %}

{% block body_block %}

<url>

    {% for drink in drinks %}

    <li class="{% cycle r y b %}">{{ drink }}</li>

</url>

{% endfor %}

{% endblock %}

(2){% cycle arg1 arg2 .. as cc %}

{% cycle %}也不一定必须要在{% for %}内，也可以放在{% for %}外，在这种情况下，每次调用{% cycle arg1,arg2 %}都返回arg1，这样就达不到循环的目的了，怎么办？此时，正是{% cycle arg1 arg2 ... as cc %} 出现的原因了，as 将{% cycle arg1 arg2 ... %} "另存为" cc，之后的事情就比较有意思：直接调用cc将只得到上次循环后的值，也就是说如果是“保存完" cc后，直接调用cc，将返回arg1，如果 {% cycle cc %}将”迫使“ cc进行循环，这时返回arg2，如果再直接调用cc呢，将返回arg2。代码的话，见下面：

# urls.py

'drinks':['water','cola','coco','milk','coffee','wanglaoji'],'r':'red','b':'blue','y':'yellow'

{% extends 'banners/base.html' %}

{% block title_block %}

test

{% endblock %}

{% block body_block %}

<url>

    <li class="{% cycle r y b  %}">test1</li>

    <li class="{% cycle r y b %}">test4</li>

    <li class="{% cycle r y b %}">test5</li>

</url>

<p>以上每次都调用'{% cycle r y b %} ' 都将是第一个参数，而不能依次取后面参数的值</p>

<url>

    <li class="{% cycle r y b as testas %}">test1</li><span>("另存为testas")</span>

    <li class="{{ testas }}">test2</li><span>(直接调用testas)</span>

    <li class="{{ testas }}">test3</li><span>(直接调用testas)</span>

    <li class="{% cycle testas %}">test4</li><span>("强迫循环")</span>

    <li class="{{ testas }}">test5</li><span>(直接调用testas)</span>

    <li class="{{ testas }}">test6</li><span>(直接调用testas)</span>

    <li class="{% cycle testas %}">test7</li><span>("强迫循环")</span>

    <li class="{{ testas }}">test8</li><span>(直接调用testas)</span>

</url>

{% endblock %}

在cc后添加 ”silent", 即{% cycle arg1 arg2 ... as cc silent %}，然后再{% cycle cc %}时，将只是个“强迫”循环的声明，而不返回任何值，见下：

#rendered.html

{% extends 'banners/base.html' %}

{% block title_block %}

test

{% endblock %}

{% block body_block %}

<url>

    <li class="{% cycle r y b  %}">test1</li>

    <li class="{% cycle r y b %}">test4</li>

    <li class="{% cycle r y b %}">test5</li>

</url>

<p>以上每次都调用'{% cycle r y b %} ' 都将是第一个参数，而不能依次取后面参数的值</p>

<url>

    <li class="{% cycle r y b as testas silent %}">test1</li><span>("仅声明循环")</span>

    <li class="{{ testas }}">test2</li><span>(直接调用testas)</span>

    <li class="{{ testas }}">test3</li><span>(直接调用testas)</span>

    <li class="{% cycle testas %}">test4</li><span>("声明循环，不返回任何值")</span>

    <li class="{{ testas }}">test5</li><span>(直接调用testas)</span>

    <li class="{{ testas }}">test6</li><span>(直接调用testas)</span>

    <li class="{% cycle testas %}">test7</li><span>("声明循环，不返回任何值")</span>

    <li class="{{ testas }}">test8</li><span>(直接调用testas)</span>

</url>

{% endblock %}

重新设置循环，将循环值重新设定为第一个，如：

#  rendered.html

{% extends 'banners/base.html' %}

{% block title_block %}

test

{% endblock %}

{% block body_block %}

<url>

    <li class="{% cycle r y b  %}">test1</li>

    <li class="{% cycle r y b %}">test4</li>

    <li class="{% cycle r y b %}">test5</li>

</url>

<p>以上每次都调用'{% cycle r y b %} ' 都将是第一个参数，而不能依次取后面参数的值</p>

<url>

    <li class="{% cycle r y b as testas %}">test1</li><span>("仅声明循环")</span>

    <li class="{{ testas }}">test2</li><span>(直接调用testas)</span>

    <li class="{{ testas }}">test3</li><span>(直接调用testas)</span>

    <li class="{% cycle testas %}">test4</li><span>("声明循环，不返回任何值")</span>

    <li class="{{ testas }}">test5</li><span>(直接调用testas)</span>

    <li class="{{ testas }}">test6</li><span>(直接调用testas)</span>

    {% resetcycle %}

    <p>resetcycle,下次循环不再是蓝色，而将是第一个值也就是红色</p>

    <li class="{% cycle testas %}">test7</li><span>("声明循环，不返回任何值")</span>

    <li class="{{ testas }}">test8</li><span>(直接调用testas)</span>

</url>

{% endblock %}

regroup 有点像 pandas里的groupby ，即通过某个属性将一群数据进行分组，不同的是该tag分组后会自动生成两个属性：①grouper：item that was grouped ② list: a list of all items in this group

# urls.py

stores=[

    {'name':'Downtown','street':'385 Main street','city':'San Diego'},

    {'name':'Uptown','street':'231 Highland avenue','city':'San Deiego'},

    {'name':'Midtown','street':'85 Balboa street','city':'Los Angeles'},

    {'name':'Downtown','street':'639 Spring street','city':'Los Angeles'},

    {'name':'Midtown','street':'1407 Broadway street','city':'Los Angeles'},

]

'stores':stores

# rendered.html

{% regroup stores by city as city_list %}

<ul>

    {% for city in city_list %}

    <li>{{ city.grouper }}</li>

    <ul>

        {% for item in city.list %}

        <li>{{ item.name }}:{{ item.street }}</li>

        {% endfor %}

    </ul>

    {% endfor %}

</ul>

Python and Filter Operations

可将包在{% filter %}....{% endfilter %}的部分内容全部进行过滤。

#urls.py

'drinks':['cola','milk','water']

#rendered.html

{% filter upper %}

{% for drink in drinks %}

{{ drink }}

{% endfor %}

{% endfilter %}

对于创建没有被view方法或者必须通过“高昂”的操作才能得到的变量，用该tag就会非常方便。

#urls.py

'drink_cost':2

#rendered.html

{% with drinktax=drink_cost drinkpro=drink_cost %}

{{ drinktax}}<br>

{{drinkpro}}

{% endwith %}

Spacing and Special Characters

在{% autoescape on %}...{% endautoescape %}之间的将被转义：

# urls.py

'drink_cost':'<b>escape?</b>'

# rendered.html

{% autoescape on %}

{{ drink_cost }}

{% endautoescape %}

{% autoescape off %}

{{ drink_cost }}

{% endautoescape %}

{% spaceless %}...

仅仅移除tag之间的空隙。
用于输出组成template tag的特殊符号：

Argument Outputs

openblock {%

closeblock %}

openvariable {{

closevariable }}

openbrace {

closebrace }

opencomment {#

closecomment #}
```
#rendered.html

{% templatetag openvariable %} url 'entry_list' {% templatetag closeblock %}
```
在{% verbatim %}...{% endverbatim %}之间的内容将被不被渲染。也可以在该tag中添加自定义的名字，即{% verbatim mytag %}...{% endverbatim %}
```
# rendered.html

{% verbatim myblock %}

    Avoid template rendering via the {% verbatim %}{% endverbatim %} block.

{% endverbatim myblock %}
```

Argument	Outputs
`openblock`	`{%`
`closeblock`	`%}`
`openvariable`	`{{`
`closevariable`	`}}`
`openbrace`	`{`
`closebrace`	`}`
`opencomment`	`{#`
`closecomment`	`#}`

{% lorem [count] [method] [random] %}

三个可选参数：

Argument	Description
`count`	A number (or variable) containing the number of paragraphs or words to generate (default is 1)
`method`	Either `w` for words, `p` for HTML paragraphs or `b` for plain-text paragraph blocks (default is `b`).
`random`	The word `random`, which if given, does not use the common paragraph (“Lorem ipsum dolor sit amet…”) when generating text.

# rendered.html

{% lorem 3 p %}

Template structures

{% comment %}...{% endcomment %}之间的将不被渲染

# rendered.html

<p>Rendered text with </p>

{% comment  %}

    <p>Commented out text with {{ create_date|date:"c" }}</p>

{% endcomment %}

{ # #}:单独一行注释

<p>Great feeling</p>

{# This is comment  #}

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