Python object-oriented Programming--__init () __ Method

Implicitly-based class object

Each Python class implicitly inherits an object

Full-Text Code example implementation: enumeration of Poker's suit and card face value

One, _init () __ Method: Object Initialization

Display instead of implicit: __init () __ should show initialization variables

When an object is instantiated, an empty object is created before calling __init () __ to initialize the object's internal variables or other content.

Second, _init () __ Method use case:

　　(i) Base class implementation initialization

1 classCard:2     def __init__(self, Rank, suit):3Self.rank =Rank4Self.suit =Suit5Self.hard, Self.soft =self._points ()6 7 8 classNumbercard (Card):9     def_points (self):Ten         returnInt (self.rank), int (Self.rank) One  A  - classAcecard (Card): -     def_points (self): the         return1, 11 -  -  - classFacecard (Card): +     def_points (self): -         return10, 10

• Three sub-classes share common initialization logic
• Polymorphic: Three subclasses have different function implementations for _points (self)

　Improved: Subclass implementation __init () __ Method

1 classCard:2     def __init__(self, rank, suit, hard, soft):3Self.rank =Rank4Self.suit =Suit5Self.hard = Hard6Self.soft =Soft7 8 9 classNumbercard (Card):Ten     def __init__(self, Rank, suit): OneSuper ().__init__(str (rank), suit, rank, rank) A  -  - classAcecard (Card): the     def __init__(self, Rank, suit): -Super ().__init__('A', suit, 1, 11) -  -  + classFacecard (Card): -     def __init__(self, Rank, suit): +Super ().__init__({1:'A', 11:'J', 12:'Q', 13:'K'}[rank], suit, 10, 10)

Super (): When a subclass is used to invoke a method with the same name as the parent class

Single Inheritance:

Call Super () directly in the same name function. Fun_name ()

Multiple inheritance:

Call super directly in the same name function (to call the previous class name of a parent class, self). Fun_name ()

　　(ii) Create a list of constants

# the character and name of the card class Suit:     def __init__ (self, Name, symbol):         = name        = Symbol

1Club, Diamond, heart, Spade = Suit ('Club','C'), Suit ('Diamond','D'),2Suit ('Heart','H'), Suit ('Spade','S')

called

Second, the factory function

Two ways to implement factory functions

• Defines a function that returns objects of different classes
• Defines a class that contains methods for creating objects

Pathway One:

1 defcard1 (rank, suit):2     ifRank = = 1:3         returnAcecard ('A', suit)4     elif2 <= Rank <= 10:5         returnNumbercard (str (rank), suit)6     elifRank = = 11:7         returnFacecard ('J', suit)8     elifRank = = 12:9         returnFacecard ('Q', suit)Ten     elifRank = = 13: One         returnFacecard ('K', suit)

The above function realizes the match of the card face value and the suit

Iii. using maps and classes to simplify design

　　(i) Parallel mapping

1 defCard2 (rank, suit):2     #find rank in the collection, not found to return Numbercard3Class_ = {1:acecard, 11:facecard, 12:facecard, 13: Facecard}.get (rank,4 Numbercard)5Rank_str = {1:'A', 11:'J', 12:'Q', 13:'K'}.get (rank, str )6     returnClass_ (RANK_STR, suit)

Cons: Mapping keys 1, 11, 12, 13, logical repetition, using two-time mappings to obtain the face value and color of the card. Duplicated code is redundant and improves maintenance costs

　　(ii) two-tuple mapping

1 #Two tuple mappings2 defCard3 (rank, suit):3Class_, rank_str = {1: (Acecard,'A'), one: (Facecard,'J'),: (Facecard,'Q'),4: (Facecard,'K')}.get (rank, (Numbercard, str (rank)))5     returnClass_ (RANK_STR, suit)

　　(iii) Partial function: partial function

How to use: Call function Fun_name (arg1,arg* ...)

Fun_name1=partial (Fun_name, arg1 ...)

Fun_name1 (arg* ...) partial function

 fromFunctoolsImportPartialdefCard4 (rank, suit): Part_class= {1:partial (Acecard,'A'), 11:partial (Facecard,'J'),                  12:partial (Facecard,'Q'), 13:partial (Facecard,'K')}. Get (rank, partial (numbercard, str ))returnPart_class (SUIT)

(iv) Factory fluent API

The API is implemented in conjunction with a two-tuple map, which sequentially invokes

1 classcardfactory:2     defrank (self, rank):3Self.class_, Self.rank_str = {41: (Acecard,'A'),5One: (Facecard,'J'),6: (Facecard,'Q'),7: (Facecard,'K')8 }.get (rank, (Numbercard, str (rank)))9         return SelfTen  One     defsuit (self, suit): A         returnSelf.class_ (SELF.RANK_STR, suit)

Python object-oriented Programming--__init () __ Method