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EX.Subclass relationships

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暮晨 2018-11-18 20:33:16 +08:00 committed by 暮晨
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@ -47,7 +47,7 @@ So, here we go...
- [> The disappearing variable from outer scope/消失的外部变量](#-the-disappearing-variable-from-outer-scope消失的外部变量) - [> The disappearing variable from outer scope/消失的外部变量](#-the-disappearing-variable-from-outer-scope消失的外部变量)
- [> When True is actually False/真亦假](#-when-true-is-actually-false真亦假) - [> When True is actually False/真亦假](#-when-true-is-actually-false真亦假)
- [> From filled to None in one instruction.../从有到无...](#-from-filled-to-none-in-one-instruction从有到无) - [> From filled to None in one instruction.../从有到无...](#-from-filled-to-none-in-one-instruction从有到无)
- [> Subclass relationships *](#-subclass-relationships-) - [> Subclass relationships/子类关系 *](#-subclass-relationships子类关系-)
- [> The mysterious key type conversion *](#-the-mysterious-key-type-conversion-) - [> The mysterious key type conversion *](#-the-mysterious-key-type-conversion-)
- [> Let's see if you can guess this?](#-lets-see-if-you-can-guess-this) - [> Let's see if you can guess this?](#-lets-see-if-you-can-guess-this)
- [Section: Appearances are deceptive!](#section-appearances-are-deceptive) - [Section: Appearances are deceptive!](#section-appearances-are-deceptive)
@ -1096,7 +1096,7 @@ None
--- ---
### > Subclass relationships * ### > Subclass relationships/子类关系 *
**Output:** **Output:**
```py ```py
@ -1109,14 +1109,14 @@ True
False False
``` ```
The Subclass relationships were expected to be transitive, right? (i.e., if `A` is a subclass of `B`, and `B` is a subclass of `C`, the `A` _should_ a subclass of `C`) 子类关系应该是可传递的, 对吧? (即, 如果 `A` 是 `B` 的子类, `B` 是 `C` 的子类, 那么 `A` _应该_ 是 `C` 的子类.)
#### 💡 Explanation: #### 💡 说明:
* Subclass relationships are not necessarily transitive in Python. Anyone is allowed to define their own, arbitrary `__subclasscheck__` in a metaclass. * Python 中的子类关系并不一定是传递的. 任何人都可以在元类中随意定义 `__subclasscheck__`.
* When `issubclass(cls, Hashable)` is called, it simply looks for non-Falsey "`__hash__`" method in `cls` or anything it inherits from. * 当 `issubclass(cls, Hashable)` 被调用时, 它只是在 `cls` 中寻找 `__hash__` 方法或者从继承的父类中寻找 `__hash__` 方法.
* Since `object` is hashable, but `list` is non-hashable, it breaks the transitivity relation. * 由于 `object` is 可散列的(hashable), 但是 `list` 是不可散列的, 所以它打破了这种传递关系.
* More detailed explanation can be found [here](https://www.naftaliharris.com/blog/python-subclass-intransitivity/). * 在[这里](https://www.naftaliharris.com/blog/python-subclass-intransitivity/)可以找到更详细的解释.
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