面向对象编程

来源：互联网发布：中国未来人口知乎编辑：程序博客网时间：2024/06/07 15:38

看一个简单的例子：

class Team():    def __init__(self):        self.name = "Tampa Bay Buccaneers"bucs = Team()print(bucs.name)'''Tampa Bay Buccaneers'''

当调用Team()函数时，会自动调用init函数，self是自动传入到init中的参数，它指向当前操作的对象。

并且可以通过init参数给对象添加属性：

class Team():    def __init__(self,name ):        self.name = namegiants = Team("New York Giants")

也可以给类创建函数，当调用函数时，会自动传入self参数，调用时不用显示的添加self参数。self用来访问当前对象的属性和方法。

实例方法（instance method）：

此处的print_name函数就是实例方法，它要显示调用，而不像init函数一样被自动调用。

class Team():    def __init__(self, name):        self.name = name    def print_name(self):        print(self.name)

一个稍微复杂一点的例子：

import csvf = open("nfl.csv", 'r') # game datanfl = list(csv.reader(f)) # The nfl data is loaded into the nfl variable.class Team():    def __init__(self, name):        self.name = name    def print_name(self):        print(self.name)    def count_total_wins(self):        count = 0        for row in nfl:            if row[2] == self.name:                count = count + 1        return countbroncos = Team("Denver Broncos")broncos_wins = broncos.count_total_wins()chiefs = Team("Kansas City Chiefs")chiefs_wins = chiefs.count_total_wins()

在上面这个例子中，我们load数据的时候是在类外部，这样共享代码的时候，别人调用nfl的时候回出错，因此我们需要将整体封装起来，包括数据的加载，在创建一个类对象的同时加载数据。

import csvclass Team():    def __init__(self, name):        self.name = name        f = open("nfl.csv", 'r')        csvreader = csv.reader(f)        self.nfl = list(csvreader)    def count_total_wins(self):        count = 0        for row in self.nfl: # 由于是对象的属性，必须加上self            if row[2] == self.name:                count = count + 1        return countjaguars = Team("Jacksonville Jaguars")jaguars_wins = jaguars.count_total_wins()

再添加一个函数（某个球队某年胜利的场次）

import csvclass Team():    def __init__(self, name):        self.name = name        f = open("nfl.csv", 'r')        csvreader = csv.reader(f)        self.nfl = list(csvreader)    def count_total_wins(self):        count = 0        for row in self.nfl:            if row[2] == self.name:                count = count + 1        return count    def count_wins_in_year(self, year):        count = 0        for row in self.nfl:            if row[2] == self.name and row[0] == year:                count += 1        return countniners = Team("San Francisco 49ers")niners_wins_2013 = niners.count_wins_in_year("2013")

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