Python OOP and MetaProgramming

Python+Deep+Dive+4.pdf
Properties
- In many languages direct access to attributes is highly discouraged Instead the convention is to make the attribute private, and create public getter and setter methods
- Python property
  - ((65211fdc-5010-4ade-975c-c0cf9b480269))
  - ((65212021-413d-4bcd-a1c1-81a964e79a45))
- property decorator @property
  - ((652120be-a7ed-40a4-9429-a7b7c1d4eb95))
- ReadOnly Properties
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Class Scope
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- ((652121e6-0bca-48f3-9aae-de800eed9d41))¶

Enumerators And Alias

Enum class

class Color(Enum):
  red = 1
  crimson = 1
  carmine = 1
  blue = 2
  black = 3

- auto values - enum.auto() generate a auto values for enum - MetaProgramming - type - type is a class

  ``` python
  class type:
    def __init__(self):
        在空值初识话数据

    def __new__(self):
          # __new__ from object
        创建->创建类
  ```
    - create a class with `type`: `type(class_name, class_base, class_dict)`
- `type` allow you create new class programmly

Metaclass
- The class used to create a class, is called metaclass of that class, e.g. MyType is metaclass of Person
- By dflt, type is used to create a new class, but now if metaclass specified, it will be replace type
- Create a new class from MyType MyType
```
class MyType(type):

    def __new__(cls, *args, **kwargs):
        xx = super().__new__(cls, *args, **kwargs)
        return xx
```
* method 1 use MyType()
```
Foo = MyType("Foo", (object,), {"v1": 123, "func": lambda self: 999})
```
* method 2 use metaclass
```
class Foo(object, metaclass=MyType):
    v1 = 123
    def func(self):
        return 999
```
- If Base class created with metaclass, all child/grandchild class of Base will be create with same metaclass - ((652124f8-b924-4054-8d9b-e56256794d28)) -

Python OOP and MetaProgramming

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