Jinja2模板注入 | python模板注入特殊属性 / 对象讲解

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在进行模板利用的时候需要使用特殊的属性和对象进行利用，这里对这些特殊属性及方法进行讲解
以下实验输出class="tags" href="/tags/PYTHON.html" title=python>python3版本为 3.10.4， class="tags" href="/tags/PYTHON.html" title=python>python2版本为 2.7.13

特殊属性

__class__ 类实例上使用，它用于获取该实例对应的类
__base__ 用于获取父类
__mro__ （Method Resolution Order）。__mro__ 属性返回一个元组，其中包含了类的继承链

特殊方法

__subclasses__() 获取直接子类

其他

__globals__ 一个特殊的变量，不使用在类上，而是用于函数，获取全局变量的字典
__builtins__ 它包含了 Python 内置的函数、异常和对象。这个模块使内置函数和对象在全局作用域中可用，无需显式导入

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👉 目录

一、特殊属性
- `__class__`
- `__base__`
- `__mro__ `
二、特殊方法
- `__subclasses__()`
三、其他
- `__globals__`
- `__builtins__ `

一、特殊属性

class_22">`class__`

使用在实例上，获取该实例对应的类

class="prism language-csharp">class="token keyword">class class="token class-name">Aclass="token punctuation">:
    class="token type-list">class="token class-name">pass

class="prism language-csharp">class="token function">printclass="token punctuation">(Aclass="token punctuation">)	# 类
class="token preprocessor property"># class="token return-type class-name">__main__class="token punctuation">.A

class="token function">printclass="token punctuation">(class="token function">Aclass="token punctuation">(class="token punctuation">)class="token punctuation">)	# 实例
class="token preprocessor property"># <__main__.A instance at 0x0000000002BA2348>

关系如下

class="prism language-csharp">class="token function">Aclass="token punctuation">(class="token punctuation">)class="token punctuation">.__class__ class="token operator">== A
class="token preprocessor property"># True

`base`

使用在类上，获取父类

class="prism language-csharp">class="token keyword">class class="token class-name">Aclass="token punctuation">:
    pass

class="token keyword">class class="token class-name">Bclass="token punctuation">(Aclass="token punctuation">)class="token punctuation">:
    pass

这里分两个情况， class="tags" href="/tags/PYTHON.html" title=python>python2和class="tags" href="/tags/PYTHON.html" title=python>python3

class="tags" href="/tags/PYTHON.html" title=python>python2

class="prism language-csharp">class="token function">printclass="token punctuation">(Bclass="token punctuation">)
class="token preprocessor property"># __main__.B

class="tags" href="/tags/PYTHON.html" title=python>python3

class="prism language-csharp">class="token function">printclass="token punctuation">(Bclass="token punctuation">)
class="token preprocessor property"># <class '__main__.B'>

我对这两个表示也不是很理解，但是只有class="tags" href="/tags/PYTHON.html" title=python>python3这种表示方式才能使用 __base__
比如class="tags" href="/tags/PYTHON.html" title=python>python3

class="prism language-csharp">class="token function">printclass="token punctuation">(Bclass="token punctuation">.__base__class="token punctuation">)
class="token preprocessor property"># <class '__main__.A'>

可以看到结果是父类 A

class="tags" href="/tags/PYTHON.html" title=python>python2我这里使用自带的类来演示
() 是tuple的实例
"" 是str的实例
[] 是list的实例

class="prism language-csharp">class="token function">printclass="token punctuation">(class="token punctuation">(class="token punctuation">)class="token punctuation">.__class__class="token punctuation">)
class="token function">printclass="token punctuation">(class="token string">""class="token punctuation">.__class__class="token punctuation">)
class="token function">printclass="token punctuation">(class="token punctuation">[class="token punctuation">]class="token punctuation">.__class__class="token punctuation">)

class="token preprocessor property"># <class 'tuple'>
class="token preprocessor property"># <class 'str'>
class="token preprocessor property"># <class 'list'>

可以发现输出的格式和class="tags" href="/tags/PYTHON.html" title=python>python3输出自定义类的相似
这里就可以使用 __base__ 了

class="prism language-csharp">class="token function">printclass="token punctuation">(class="token punctuation">(class="token punctuation">)class="token punctuation">.__class__class="token punctuation">.__base__class="token punctuation">)
class="token preprocessor property"># <class 'object'>

`mro`

返回类的继承链

class="prism language-csharp">class="token keyword">class class="token class-name">Aclass="token punctuation">:
    pass

class="token keyword">class class="token class-name">Bclass="token punctuation">(Aclass="token punctuation">)class="token punctuation">:
    pass

class="token keyword">class class="token class-name">Cclass="token punctuation">(Bclass="token punctuation">)class="token punctuation">:
    pass

这里使用class="tags" href="/tags/PYTHON.html" title=python>python3演示，因为要以下输出格式才有效

class="prism language-csharp">class="token operator"><class="token keyword">class 'xxx'class="token operator">>

class="tags" href="/tags/PYTHON.html" title=python>python2 创建自定义类时没有这种效果

class="prism language-csharp">class="token function">printclass="token punctuation">(Cclass="token punctuation">.__mro__class="token punctuation">)
class="token preprocessor property"># (<class '__main__.C'>, <class '__main__.B'>, <class '__main__.A'>, <class 'object'>)

创建类时默认继承Object，所以继承链一共有3个对象
在这里插入图片描述

如果B此时多继承个D，那么C.__mro__ 就会有4个对象
在这里插入图片描述

二、特殊方法

classes_137">`subclasses__()`

获取直接子类
和 __mro__不同，__subclasses__() 是一个方法，获取直接子类

class="prism language-csharp">class="token keyword">class class="token class-name">Aclass="token punctuation">:
    pass

class="token keyword">class class="token class-name">Bclass="token punctuation">(Aclass="token punctuation">)class="token punctuation">:
    pass

class="token keyword">class class="token class-name">Cclass="token punctuation">(Bclass="token punctuation">)class="token punctuation">:
    pass

class="token keyword">class class="token class-name">Dclass="token punctuation">(Aclass="token punctuation">)class="token punctuation">:
    pass

在这里插入图片描述
这里同样使用class="tags" href="/tags/PYTHON.html" title=python>python3做演示，返回的是一个列表

class="prism language-csharp">class="token function">printclass="token punctuation">(Aclass="token punctuation">.class="token function">__subclasses__class="token punctuation">(class="token punctuation">)class="token punctuation">)
class="token preprocessor property"># [<class '__main__.B'>, <class '__main__.D'>]

三、其他

`globals`

一个特殊的变量，不使用在类上，而是用于函数，获取全局变量的字典

class="prism language-csharp">hello class="token operator">= class="token string">"hello"
world class="token operator">= class="token string">"world"

class="prism language-csharp">class="token function">printclass="token punctuation">(testclass="token punctuation">.__globals__class="token punctuation">)
class="token preprocessor property"># {'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x00000211AE5D4A60>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, '__file__': 'C:\\Users\\wlb\\Desktop\\test\\class="tags" href="/tags/PYTHON.html" title=python>python\\7.py', '__cached__': None, 'hello': 'hello', 'world': 'world', 'test': <function test at 0x00000211AE173E20>}

可以看到有很多键值对，几个熟悉的键值对

class="prism language-csharp">'hello'class="token punctuation">: 'hello'class="token punctuation">, 
'world'class="token punctuation">: 'world'class="token punctuation">, 
'test'class="token punctuation">: class="token operator"><function test at class="token number">0x000001FDD5E23E20class="token operator">>

上面有的键都可以直接使用 print打印出来
比如最常见的

class="prism language-csharp">class="token function">printclass="token punctuation">(__name__class="token punctuation">)

`builtins`

它包含了 Python 内置的函数、异常和对象。这个模块使内置函数和对象在全局作用域中可用，无需显式导入

我们直接可以使用的函数和对象都在该变量上

class="prism language-csharp">class="token function">printclass="token punctuation">(__builtins__class="token punctuation">.print class="token operator">== printclass="token punctuation">)
class="token preprocessor property"># True