《Django 5 By Example》学习第 19 天，p543-p550 总结，总计 8 页。
一、技术总结
1.fixtures
(1)定义
A fixture is a collection of files that contain the serialized contents of the database.
(2)作用
1)数据导入
一般来说，我们是通过数据库工具(如：Navicat，DBeaver)进行数据导入和导出。在 Django中，也可以通过 fixtures 结合 duamdata 、loaddata 命令进行数据导入导出。
单纯从数据导入导出这点来说，我更倾向于使用数据库工具进行操作，因为这更通用。
(3)示例
注：educa是 project， courses 是 application。
python
educa# mkdir courses/fixture
educa# python manage.py dumpdata courses --indent=2 --output=courses/fixtures/subjects.json
educa# python manage.py loaddata subjects.json2.model inheritance
Django中有三种类型 model inheritance:
(1)abstract model
(2)multi-table model inheritance
(3)proxy model
二、英语总结(生词：2)
1.polymorphism
(1)polymorph
poly-("many") + morph("form, shape")
(2)polymorphism: polymorph + -ism
u. the fact the sth can exist in different forms(多态性)。
(3)polymorphous vs polymorphic
adj. having many different forms(多态的)。polymorphous 和 polymorphic的意思是一样的，他们之间的区别是：
1)polymorphous
Commonly used as a descriptive term in general contexts, including art, literature, and natural sciences.
示例：Water is a polymorphous substance, taking the form of ice, liquid, or vapor.
2)polymorphic
Often used in technical or scientific contexts, such as programming, biology, or chemistry.
示例：The class exhibits polymorphic behavior by overriding methods in different subclasses.
2.provision
(1)provision: pro-("before, forward") + vision(from videre, "to see")
字面意思是"to see beforehand(预先看看)"， "to prepare in advance(提前准备)"，后面演变为：c/u. the act of providing sth。
(2)provide: provision 是 provide 的名词形式。
p546, Polymorphism is the provision of a single interface to entities of different types（多态是为不同类型的实体提供单一接口）.
三、其它
今天没有什么想说的。
四、参考资料
1. 编程
(1) Antonio Melé，《Django 5 By Example》：https://book.douban.com/subject/37007362/
2. 英语
(1) Etymology Dictionary：https://www.etymonline.com
(2) Cambridge Dictionary：https://dictionary.cambridge.org
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