Django中的内置Tags

Dates

{% now %}
```
{% 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{% else %}

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{% for %}

#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 %}

{% cycle %}

(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 %}

{% resetcycle %}

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 %}

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

{% filter %}

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 %}

{% with %}

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

{% autoescape %}

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 %}...{% endspaceless %}

仅仅移除tag之间的空隙。
{% templatetag %}

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 %}
```
{% verbatim %}

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 *}

{% 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

{% block %}

{% 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  #}

{% extends %}
{% include %}
{% load %}

URLs
{% url %}

##### 愿你一寸一寸地攻城略地，一点一点地焕然一新 #####