性xxxx欧美老肥妇牲乱,91精品国产成人观看,波多野结衣中文字幕一区

主頁 > 知識庫 > python接口,繼承,重載運(yùn)算符詳解

python接口,繼承,重載運(yùn)算符詳解

1. 序列getitem

如果沒有 __iter__ 和 __contains__ 方法，
Python 會調(diào)用 __getitem__ 方法，
設(shè)法讓迭代和 in 運(yùn)算符可用

class Foo:
    def __getitem__(self, pos):
        return range(0, 30, 10)[pos]

f = Foo()
print(f[1])  # 10
for i in f:
    print(i)  # 0, 10, 20
# 如果沒有 __iter__ 和 __contains__ 方法，
# Python 會調(diào)用 __getitem__ 方法，
# 設(shè)法讓迭代和 in 運(yùn)算符可用

2. setitem

import collections
Card = collections.namedtuple('Card', ['rank', 'suit'])

class FrenchDeck:
    ranks = [str(n) for n in range(2, 11)] + list('JQKA')
    suits = 'spades diamonds clubs hearts'.split()
    def __init__(self):
        self._cards = [Card(rank, suit) for suit in self.suits for rank in self.ranks]
    def __len__(self):
        return len(self._cards)
    def __getitem__(self, position):
        return self._cards[position]
	def __str__(self):
        return ",".join(str(i) for i in self._cards)
from random import shuffle
deck = FrenchDeck()
print(str(deck))
# Card(rank='2', suit='spades'),Card(rank='3', suit='spades'),Card(rank='4', suit='spades'),Card(rank='5', suit='spades'),Card(rank='6', suit='spades'),Card(rank='7', suit='spades'),Card(rank='8', suit='spades'),Card(rank='9', suit='spades'),Card(rank='10', suit='spades'),Card(rank='J', suit='spades'),Card(rank='Q', suit='spades'),Card(rank='K', suit='spades'),Card(rank='A', suit='spades'),Card(rank='2', suit='diamonds'),Card(rank='3', suit='diamonds'),Card(rank='4', suit='diamonds'),Card(rank='5', suit='diamonds'),Card(rank='6', suit='diamonds'),Card(rank='7', suit='diamonds'),Card(rank='8', suit='diamonds'),Card(rank='9', suit='diamonds'),Card(rank='10', suit='diamonds'),Card(rank='J', suit='diamonds'),Card(rank='Q', suit='diamonds'),Card(rank='K', suit='diamonds'),Card(rank='A', suit='diamonds'),Card(rank='2', suit='clubs'),Card(rank='3', suit='clubs'),Card(rank='4', suit='clubs'),Card(rank='5', suit='clubs'),Card(rank='6', suit='clubs'),Card(rank='7', suit='clubs'),Card(rank='8', suit='clubs'),Card(rank='9', suit='clubs'),Card(rank='10', suit='clubs'),Card(rank='J', suit='clubs'),Card(rank='Q', suit='clubs'),Card(rank='K', suit='clubs'),Card(rank='A', suit='clubs'),Card(rank='2', suit='hearts'),Card(rank='3', suit='hearts'),Card(rank='4', suit='hearts'),Card(rank='5', suit='hearts'),Card(rank='6', suit='hearts'),Card(rank='7', suit='hearts'),Card(rank='8', suit='hearts'),Card(rank='9', suit='hearts'),Card(rank='10', suit='hearts'),Card(rank='J', suit='hearts'),Card(rank='Q', suit='hearts'),Card(rank='K', suit='hearts'),Card(rank='A', suit='hearts')
shuffle(deck)  # TypeError: 'FrenchDeck' object does not support item assignment

加入__setitem__

    def __setitem__(self, key, value):
        self._cards[key] = value

shuffle(deck) 
print(str(deck))
# 牌被隨機(jī)打亂了
# Card(rank='6', suit='hearts'),Card(rank='2', suit='spades'),Card(rank='3', suit='hearts'),Card(rank='A', suit='clubs'),Card(rank='7', suit='clubs'),Card(rank='Q', suit='diamonds'),Card(rank='5', suit='hearts'),Card(rank='6', suit='spades'),Card(rank='5', suit='diamonds'),Card(rank='8', suit='diamonds'),Card(rank='K', suit='hearts'),Card(rank='Q', suit='hearts'),Card(rank='8', suit='hearts'),Card(rank='3', suit='diamonds'),Card(rank='Q', suit='clubs'),Card(rank='A', suit='diamonds'),Card(rank='9', suit='hearts'),Card(rank='7', suit='diamonds'),Card(rank='A', suit='spades'),Card(rank='J', suit='hearts'),Card(rank='3', suit='clubs'),Card(rank='4', suit='hearts'),Card(rank='Q', suit='spades'),Card(rank='10', suit='diamonds'),Card(rank='10', suit='hearts'),Card(rank='K', suit='diamonds'),Card(rank='2', suit='diamonds'),Card(rank='4', suit='spades'),Card(rank='3', suit='spades'),Card(rank='7', suit='hearts'),Card(rank='9', suit='clubs'),Card(rank='J', suit='clubs'),Card(rank='J', suit='diamonds'),Card(rank='10', suit='spades'),Card(rank='4', suit='diamonds'),Card(rank='7', suit='spades'),Card(rank='9', suit='diamonds'),Card(rank='2', suit='hearts'),Card(rank='6', suit='clubs'),Card(rank='K', suit='clubs'),Card(rank='4', suit='clubs'),Card(rank='A', suit='hearts'),Card(rank='K', suit='spades'),Card(rank='2', suit='clubs'),Card(rank='J', suit='spades'),Card(rank='8', suit='spades'),Card(rank='5', suit='spades'),Card(rank='9', suit='spades'),Card(rank='10', suit='clubs'),Card(rank='8', suit='clubs'),Card(rank='6', suit='diamonds'),Card(rank='5', suit='clubs')

或者在類外打補(bǔ)丁 FrenchDeck.__setitem__ = 函數(shù)

def set_card(deck, position, card):
    deck._cards[position] = card

FrenchDeck.__setitem__ = set_card

3. 抽象基類

class Test:
    def __len__(self):
        return 24

from collections import abc
print(isinstance(Test(), abc.Sized)) # True

只要實(shí)現(xiàn)了 __len__() 方法，就可以被 abc.Sized 識別為子類

4. 不要直接子類化內(nèi)置類型

class AnswerDict(dict):
    def __getitem__(self, key):
        return 24

ad = AnswerDict(a="good")
print(ad['a'])  # 24
d = {}
d.update(ad)
print(d['a'])  # good
print(ad)  # {'a': 'good'}
print(d)  # {'a': 'good'}

直接子類化內(nèi)置類型（如 dict、list 或 str）容易出錯(cuò)，因?yàn)?內(nèi)置類型的方法通常會忽略用戶覆蓋的方法。

不要子類化內(nèi)置類型，用戶自己定義的類應(yīng)該繼承 collections 模塊中的類，例如 UserDict、UserList 和 UserString，這些類做了特殊設(shè)計(jì)，因此易于擴(kuò)展

5. 繼承順序

import collections

class AnswerDict2(collections.UserDict):
    def __getitem__(self, key):
        return 24
ad = AnswerDict2(a="good")
print(ad['a'])  # 24
d = {}
d.update(ad)
print(d['a'])  # 24
print(ad)  # {'a': 'good'}
print(d)  # {'a': 24}

多重繼承的同名方法調(diào)用，根據(jù)類的 __mro__ 屬性順次在類中查找
推薦使用 super() 函數(shù)

6. 重載運(yùn)算符

不可變類型，，一定不能實(shí)現(xiàn)就地特殊方法

__iadd__等增量賦值特殊方法必須返回 self

總結(jié)

本篇文章就到這里了，希望能給你帶來幫助，也希望您能夠多多關(guān)注腳本之家的更多內(nèi)容！

您可能感興趣的文章:

python面向?qū)ο笾惖睦^承詳解
Python面向?qū)ο笾^承代碼詳解
Python面向?qū)ο缶幊讨^承與多態(tài)詳解
Python類的繼承和多態(tài)代碼詳解
Python 的類、繼承和多態(tài)詳解
python的繼承詳解

標(biāo)簽：海南大同寧夏漯河盤錦普洱林芝南平

巨人網(wǎng)絡(luò)通訊聲明：本文標(biāo)題《python接口,繼承,重載運(yùn)算符詳解》，本文關(guān)鍵詞 python,接口,繼承,重載,運(yùn)算符,；如發(fā)現(xiàn)本文內(nèi)容存在版權(quán)問題，煩請?zhí)峁┫嚓P(guān)信息告之我們，我們將及時(shí)溝通與處理。本站內(nèi)容系統(tǒng)采集于網(wǎng)絡(luò)，涉及言論、版權(quán)與本站無關(guān)。