1.0 GENERAL grammar

Only need to remember two special symbols:

{{ }}with {% %}

Variable associated with {{}}, {logic associated with %%}.

1.1 Variable

Click Django template language syntax used in: {{name}} variable.

When the template engine encounters a variable, it will calculate the variable, and then replace it with the result itself. Named variables include any alphanumeric and underscore ( "_") combination. Variable names can not contain spaces or punctuation.

Dot (.) Has a special meaning in the template language. When the template system encounters a dot ( "."), It will be in this order inquiries:

Dictionary lookup (Dictionary lookup)
property or method query (Attribute or method lookup)
digital index query (Numeric index lookup)

Precautions:

If the value of calculation result is called, it will be invoked with no parameters. Result of the call will be the value of the template.
If variables does not exist, the system will insert the value string_if_invalid template option, which is the default setting is '' (the empty string).

A few examples:

view code:

def template_test(request):
    l = [11, 22, 33]
    d = {"name": "alex"}

    class Person(object):
        def __init__(self, name, age):
            self.name = name
            self.age = age

        def dream(self):
            return "{} is dream...".format(self.name)

    Alex = Person(name="Alex", age=34)
    Egon = Person(name="Egon", age=9000)
    Eva_J = Person(name="Eva_J", age=18)

    person_list = [Alex, Egon, Eva_J]
    return render(request, "template_test.html", {"l": l, "d": d, "person_list": person_list})

Template support wording:

{ # Take the first parameter l} # 
{l.0} {} 
{ # take the dictionary key value} # 
{d.name} {} 
{ # take the object name attribute} # 
{{person_list.0 }} .name 
{ # . # operation method can only be called with no arguments} 
{} {} person_list.0.dream

1.2 Filters Filters

In Django template language by using filters to change the display of variables.

The syntax of the filter: {{value | filter_name: Parameter}}

Use pipe symbol "|" applying a filter.

For example: {{name | lower}} then the variable name will show its value after the application of lower filter. lower in action here is all lowercase text.

Precautions:

Filter supports the "chain" operation. I.e., a filter output as input to another filter.
Filters can accept parameters, for example: {{sss | truncatewords: 30}}, which will display the first 30 words of sss.
Filter parameter contains a space, it must be wrapped in quotes. Such as comma and a space used to connect the elements of a list, such as: {{list | join: ','}}
'|' Around is no space without a space with no spaces

Django template language provides about sixty built-in filter.

default

If a variable is false or empty, the default values given. Otherwise, use the value of the variable.

{{ value|default:"nothing"}}

If value is null or the value is not passed, then nothing is displayed

length

Returns the length, acting on the string and the value list.

{{ value|length }}

filesizeformat

Value formatted as a "human readable" file size (e.g. '13 KB', '4.1 MB', '102 bytes', etc.). E.g

{{ value|filesizeformat }}

slice

{{value|slice:"2:-1"}}

date

format

{{ value|date:"Y-m-d H:i:s"}}

Available parameters:

Formatting characters	description	Sample output
a	`'a.m.'`Or `'p.m.'`(Note that this is slightly different with PHP's output, because this includes the period in line with Associated Press style)	`'a.m.'`
A	`'AM'`Or `'PM'`.	`'AM'`
b	Month, word, three letters, lowercase.	`'jan'`
B	Unrealized.
c	ISO 8601 format. (Note: Unlike other formatting procedures, for example, "Z", "O" or "r", if the value naive datetime, the "c" format program does not add time zone offset	`2008-01-02T10:30:00.000123+02:00`Or `2008-01-02T10:30:00.000123`if naive datetime
d	May the day with 2 digits with leading zeros.	`'01'`To`'31'`
D	Word of the week, three letters.	`“星期五”`
e	Time zone name may be in any format, or may return a null string, depending datetime.	`''`, `'GMT'`, `'-500'`, `'US/Eastern'`Etc.
E	Month, instead of specific regions commonly used to represent long date representation.	`'listopada'`(For Polish regions, not `'Listopad'`)
f	Time, within 12 hours hours and minutes, if they are zero, the minute hold. Proprietary extensions.	`'1'`，`'1:30'`
F	Month, text, long.	`'一月'`
g	Hour, 12-hour format, without leading zeros.	`'1'`To`'12'`
G	Hour, 24-hour format, without leading zeros.	`'0'`To`'23'`
h	Hour, 12-hour format.	`'01'`To`'12'`
H	Hour, 24-hour format.	`'00'`To`'23'`
i	minute.	`'00'`To`'59'`
I	Daylight Saving Time, regardless of whether or not to take effect.	`'1'`or`'0'`
j	No day leading zeros of the month.	`'1'`To`'31'`
l	Day of the week, word length.	`'星期五'`
L	Whether the Boolean value is a leap year.	`True`or`False`
m	Month, 2 digits with leading zeros.	`'01'`To`'12'`
M	Month, word, three letters.	`“扬”`
n	Months No leading zeros.	`'1'`To`'12'`
N	Associated Press style abbreviation for the month. Proprietary extensions.	`'Jan.'`，`'Feb.'`，`'March'`，`'May'`
O	ISO-8601 week number corresponding to the number of weeks using the leap (W) ISO-8601. For the more common year format, see Y.	`'1999年'`
O	Greenwich Mean Time difference within a few hours.	`'+0200'`
P	For 12 hours, minutes and 'am. '/' pm. ', If the zero minute hold, in special circumstances the string "midnight" and the "noon." Proprietary extensions.	`'1 am'`，`'1:30 pm' / t3>，'midnight'，'noon'，'12：30 pm' / T10>`
r	Formatting date.	`'Thu, 21 Dec 2000 16:01:07 +0200'`
s	Seconds, 2 digits with leading zeros.	`'00'`To`'59'`
S	English ordinal suffix month, two characters.	`'st'`, `'nd'`, `'rd'`Or`'th'`
t	To the number of days in a given month.	`28` to `31`
T	Time zone of the machine.	`'EST'`，`'MDT'`
in	Microseconds.	`000000` to `999999`
The	Since one-half the Unix Epoch (January 1 1970 00:00:00 UTC).
w	Day of the week, digits without leading zeroes.	`'0'`(Sunday) to `'6'`(Saturday)
W	ISO-8601 a few weeks, weeks starting on Monday.	`1`，`53`
Y	Year, 2 digits.	`'99'`
Y	Year 4 digits.	`'1999年'`
with	Day of the year	`0`To`365`
WITH	Time zone offset, in seconds. Time zone UTC offset is always a negative west, east to UTC time, they are always positive.	`-43200`To`43200`

safe

Django的模板中会对HTML标签和JS等语法标签进行自动转义，原因显而易见，这样是为了安全。但是有的时候我们可能不希望这些HTML元素被转义，比如我们做一个内容管理系统，后台添加的文章中是经过修饰的，这些修饰可能是通过一个类似于FCKeditor编辑加注了HTML修饰符的文本，如果自动转义的话显示的就是保护HTML标签的源文件。为了在Django中关闭HTML的自动转义有两种方式，如果是一个单独的变量我们可以通过过滤器“|safe”的方式告诉Django这段代码是安全的不必转义。

比如：

value = "<a href='#'>点我</a>"

{{ value|safe}}

truncatechars

如果字符串字符多于指定的字符数量，那么会被截断。截断的字符串将以可翻译的省略号序列（“...”）结尾。

参数：截断的字符数

{{ value|truncatechars:9}}

truncatewords

在一定数量的字后截断字符串。

{{ value|truncatewords:9}}

cut

移除value中所有的与给出的变量相同的字符串

{{ value|cut:' ' }}

join

使用字符串连接列表，例如Python的str.join(list)

timesince

将日期格式设为自该日期起的时间（例如，“4天，6小时”）。

采用一个可选参数，它是一个包含用作比较点的日期的变量（不带参数，比较点为现在）。例如，如果blog_date是表示2006年6月1日午夜的日期实例，并且comment_date是2006年6月1日08:00的日期实例，则以下将返回“8小时”：

{{ blog_date|timesince:comment_date }}

分钟是所使用的最小单位，对于相对于比较点的未来的任何日期，将返回“0分钟”。

timeuntil

似于timesince，除了它测量从现在开始直到给定日期或日期时间的时间。例如，如果今天是2006年6月1日，而conference_date是保留2006年6月29日的日期实例，则{{ conference_date | timeuntil }}将返回“4周”。

使用可选参数，它是一个包含用作比较点的日期（而不是现在）的变量。如果from_date包含2006年6月22日，则以下内容将返回“1周”：

{{ conference_date|timeuntil:from_date }}

自定义filter

自定义过滤器只是带有一个或两个参数的Python函数:

变量（输入）的值 - -不一定是一个字符串
参数的值 - 这可以有一个默认值，或完全省略

例如，在过滤器{{var | foo:'bar'}}中，过滤器foo将传递变量var和参数“bar”。

自定义filter代码文件摆放位置：

app01/
    __init__.py
    models.py
    templatetags/  # 在app01下面新建一个package package
        __init__.py
        app01_filters.py  # 建一个存放自定义filter的文件
    views.py

编写自定义filter

from django import template
register = template.Library()


@register.filter(name="cut")
def cut(value, arg):
    return value.replace(arg, "")


@register.filter(name="addSB")
def add_sb(value):
    return "{} SB".format(value)

使用自定义filter

{# 先导入我们自定义filter那个文件 #}
{% load app01_filters %}

{# 使用我们自定义的filter #}
{{ somevariable|cut:"0" }}
{{ d.name|addSB }}

1.3 Tags

for循环

普通for循环

<ul>
{% for user in user_list %}
    <li>{{ user.name }}</li>
{% endfor %}
</ul>

for循环可用的一些参数：

Variable	Description
`forloop.counter`	当前循环的索引值（从1开始）
`forloop.counter0`	当前循环的索引值（从0开始）
`forloop.revcounter`	当前循环的倒序索引值（从1开始）
`forloop.revcounter0`	当前循环的倒序索引值（从0开始）
`forloop.first`	当前循环是不是第一次循环（布尔值）
`forloop.last`	当前循环是不是最后一次循环（布尔值）
`forloop.parentloop`	本层循环的外层循环

for ... empty

<ul>
{% for user in user_list %}
    <li>{{ user.name }}</li>
{% empty %}
    <li>空空如也</li>
{% endfor %}
</ul>

if判断

if,elif和else

{% if user_list %}
  用户人数：{{ user_list|length }}
{% elif black_list %}
  黑名单数：{{ black_list|length }}
{% else %}
  没有用户
{% endif %}

当然也可以只有if和else

{% if user_list|length > 5 %}
  七座豪华SUV
{% else %}
    黄包车
{% endif %}

if语句支持 and 、or、==、>、<、!=、<=、>=、in、not in、is、is not判断。

with

定义一个中间变量，多用于给一个复杂的变量起别名。

注意等号左右不要加空格。

{% with total=business.employees.count %}
    {{ total }} employee{{ total|pluralize }}
{% endwith %}

csrf_token

这个标签用于跨站请求伪造保护。

在页面的form表单里面写上{% csrf_token %}

注释

{# ... #}

1.4 母版

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="x-ua-compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Title</title>
  {% block page-css %}
  
  {% endblock %}
</head>
<body>

<h1>这是母板的标题</h1>

{% block page-main %}

{% endblock %}
<h1>母板底部内容</h1>
{% block page-js %}

{% endblock %}
</body>
</html>

1.5 继承母版

在子页面中在页面最上方使用下面的语法来继承母板。

{% extends 'layouts.html' %}

1.6 块（block）

通过在母板中使用{% block xxx %}来定义"块"。

在子页面中通过定义母板中的block名来对应替换母板中相应的内容。

{% block page-main %}
  <p>世情薄</p>
  <p>人情恶</p>
  <p>雨送黄昏花易落</p>
{% endblock %}

1.7 组件

可以将常用的页面内容如导航条，页尾信息等组件保存在单独的文件中，然后在需要使用的地方按如下语法导入即可。

{% include 'navbar.html' %}

1.8 静态文件相关

{% static %}

{% load static %}
<img src="{% static "images/hi.jpg" %}" alt="Hi!" />

引用JS文件时使用：

{% load static %}
<script src="{% static "mytest.js" %}"></script>

某个文件多处被用到可以存为一个变量

{% load static %}
{% static "images/hi.jpg" as myphoto %}
<img src="{{ myphoto }}"></img>

{% get_static_prefix %}

{% load static %}
<img src="{% get_static_prefix %}images/hi.jpg" alt="Hi!" />

1.9 simple_tag

和自定义filter类似，只不过接收更灵活的参数。

定义注册simple_tag

@register.simple_tag(name="plus")
def plus(a, b, c):
    return "{} + {} + {}".format(a, b, c)

　使用自定义simple_tag

{% load app01_demo %}

{# simple tag #}
{% plus "1" "2" "abc" %}

1.10 inclusion_tag

多用于返回html代码片段

示例：

templatetags/my_inclusion.py

from django import template

register = template.Library()


@register.inclusion_tag('result.html')
def show_results(n):
    n = 1 if n < 1 else int(n)
    data = ["第{}项".format(i) for i in range(1, n+1)]
    return {"data": data}

　　templates/snippets/result.html

<ul>
  {% for choice in data %}
    <li>{{ choice }}</li>
  {% endfor %}
</ul>

　　templates/index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="x-ua-compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>inclusion_tag test</title>
</head>
<body>

{% load inclusion_tag_test %}

{% show_results 10 %}
</body>
</html>

Diango template layer