mirror of https://github.com/TwoWater/Python
28 lines
1.1 KiB
Markdown
28 lines
1.1 KiB
Markdown
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# 二、Enum 的源码 #
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通过上面的实例可以知道通过 `__members__` 可以遍历枚举类的所有成员。那为什么呢？
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我们可以先来大致看看 Enum 的源码是如何实现的；Enum 在模块 enum.py 中，先来看看 Enum 类的片段
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```python
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class Enum(metaclass=EnumMeta):
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"""Generic enumeration.
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Derive from this class to define new enumerations.
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"""
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```
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可以看到，Enum 是继承元类 EnumMeta 的；再看看 EnumMeta 的相关片段
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```python
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class EnumMeta(type):
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"""Metaclass for Enum"""
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@property
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def __members__(cls):
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"""Returns a mapping of member name->value.
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This mapping lists all enum members, including aliases. Note that this
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is a read-only view of the internal mapping.
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"""
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return MappingProxyType(cls._member_map_)
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```
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首先 `__members__` 方法返回的是一个包含一个 Dict 既 Map 的 MappingProxyType，并且通过 @property 将方法 `__members__(cls)` 的访问方式改变为了变量的的形式，既可以直接通过 `__members__` 来进行访问了
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