抽象基本類的幾大特點：
1：要定義但是並不完整的實現所有方法
2：基本的意思是作為父類
3：父類需要明確表示出那些方法的特征，這樣在寫子類時更加簡單明白
用抽象基本類的地方：
1：用作父類
2：用作檢驗實例類型
3：用作拋出異常說明
關於抽象基本類的幾點說明：
1：LSP(裡式替換原則)：
子類必須能夠替換他們的基類型，替換後軟件運行形態不變，覺察不出基類和子類的區別。
這樣來檢驗該設計是否合理或者藏有缺陷。（從抽象類繼承而不是具體類）
2：關於isinstance的使用：
首先：大量的isinstance檢測會造成復雜而緩慢的程序還表明多態設計不好
其次：在使用isinstance時更加pythonic的用法是處理錯誤而不是請求許可
1:請求許可：
assert isinstance( some_argument, collections.abc.Container ),"{0!r} not a Container".format(some_argument)
盡管很簡潔，但是有兩個缺點: assertions can be silenced, and it would probably be better to raise a TypeError for this：
if not isinstance(some_argument, collections.abc.Container):
raise TypeError( "{0!r} not a Container".format(some_argument))
2：處理異常
try:
found = value in some_argument
except TypeError:
if not isinstance(some_argument, collections.abc.Container):
warnings.warn( "{0!r} not a Container".format(some_argument) )
raise
3：Containers and collections
container(容器),既是其可以包含多個對象，其實是多個reference的集合的概念,python內置的containers有比如list，map，set.
collections是python內建的一個集合模塊，提供了許多可用的集合類，如namedtuple，deque，defalutdict等等。
總結：container是一個抽象類而collections是繼承了container並實現了多種子類數據結構如namedtuple，deque，chainmap，counter，ordereddict，defaultdict的類的統稱
container應該實現的：
Lower-level features include Container, Iterable, and Sized.
they require a few specific methods, particularly __contains__(), __iter__(), and __len__(), respectively
collections應該實現的：
Sequence and MutableSequence: These are the abstractions of the concrete classes list and tuple. Concrete sequence implementations also include bytes and str.
MutableMapping: This is the abstraction of dict. It extends Mapping, but there's no built-in concrete implementation of this.
Set and MutableSet: These are the abstractions of the concrete classes,frozenset and set.
This allows us to build new classes or extend existing classes and maintain a clear and formal integration with the rest of Python's built-in features.
python中兩大抽象基類：
1：各種數據類型相關的collections.abc
>>> abs(3)
3
>>> isinstance(abs, collections.abc.Callable)
True
>>> isinstance( {}, collections.abc.Mapping )
True
>>> isinstance( collections.defaultdict(int), collections.abc.Mapping)
True
2：數值相關的numbers
>>> import numbers, decimal
>>> isinstance( 42, numbers.Number )
True
>>> isinstance( 355/113, numbers.Number ) #由此可見，integer和float都是number.Number類的子類
True
>>> issubclass( decimal.Decimal, numbers.Number ) #decimal.Decimal是numbers.Number的子類
True
>>> issubclass( decimal.Decimal, numbers.Integral )
False
>>> issubclass( decimal.Decimal, numbers.Real )
False
>>> issubclass( decimal.Decimal, numbers.Complex )
False
>>> issubclass( decimal.Decimal, numbers.Rational )
False
來看一個簡單的抽象類
__dict__：方法名+屬性名
__mro__: 包含此類所有父類的元祖
>>> class aha(list):
def __init__(self,value):
super().__init__(value)
>>> a=aha('pd')
>>> a
['p', 'd']
>>> aha.__dict__
mappingproxy({'__weakref__': <attribute '__weakref__' of 'aha' objects>, '__doc__': None, '__module__': '__main__', '__dict__': <attribute '__dict__' of 'aha' objects>, '__init__': <function aha.__init__ at 0x030967C8>})
>>> aha.__mro__
(<class '__main__.aha'>, <class 'list'>, <class 'object'>)
__dict__與__mro__
from abc import ABCMeta, abstractmethod
class AbstractBettingStrategy(metaclass=ABCMeta):
__slots__ = ()
@abstractmethod
def bet(self, hand):
return 1
@abstractmethod
def record_win(self, hand):
pass
@abstractmethod
def record_loss(self, hand):
pass
@classmethod #檢查了三個用抽象方法在子類中是否implement，否則報錯。
def __subclasshook__(cls, subclass):
if cls is Hand:
if (any("bet" in B.__dict__ for B in subclass.__mro__) and any("record_win" in B.__dict__ for B in subclass.__mro__) and any("record_loss" in B.__dict__ for B in subclass.__mro__)):
return True
return NotImplemented
class Simple_Broken(AbstractBettingStrategy):
def bet( self, hand ):
return 1
# The preceding code can't be built because it doesn't provide necessary implementations for all three methods.
# The following is what happens when we try to build it:
>>> simple= Simple_Broken()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Can't instantiate abstract class Simple_Broken with
abstract methods record_loss, record_win
#注，上例可能太過嚴格，有些子類並不需要實現其所有方法，這個需要具體情況再看
#注，此篇可能看起來有點不太邏輯清晰，這源於我對collections.abc以及number模塊目前還不太清晰，等改天研究明白了來改改，加些內容，此時先放出來占個位
