python 类相关概念理解

class CLanguage :
    # 下面定义了2个类变量
    name = "python语言"
    add = "http://c.biancheng.net.python"
    # __init__是构造方法，也属于实例方法  
    def __init__(self,name,add):
        #下面定义 2 个实例变量
        self.name = name
        self.add = add
        print(name,"网址为：",add)
    # 下面定义了一个say实例方法
    def say(self, content):
        print(content)
    #下面定义了一个count实例方法   
    def count(self,money):
    #下面定义了一个局部变量sale
        sale = 0.8*money
        print("优惠后的价格为：",sale)
    #下面定义了一个类方法
    @classmethod
    def info(cls):
        print("正在调用类方法",cls)
    #下面定义了一个静态方法
    @staticmethod
    def info(name,add):
        print(name,add)
# 将该CLanguage对象赋给clanguage变量
# 通过类名直接调用实例方法
# CLanguage.say("通过类名直接调用实例方法")会报错，必须手动将 clang 这个类对象传给self 参数
clang = CLanguage("C语言中文网1","http://c.biancheng.net")#传入的参数要和init的一样
CLanguage.say(clang, "通过类名直接调用实例方法")
# 通过类对象直接调用实例方法
clang2 = CLanguage("C语言中文网2","http://c.biancheng.net")
clang2.say("通过类对象直接调用实例方法")

#输出
C语言中文网1 网址为： http://c.biancheng.net
通过类名直接调用实例方法
C语言中文网2 网址为： http://c.biancheng.net
通过类对象直接调用实例方法

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
    def print_title(self):
        if self.sex == "male":
            print("man")
        elif self.sex == "female":
            print("woman")
class Child(Person):                            # Child 继承 Person
    pass
May = Child("May","female")
Peter = Person("Peter","male")
print(May.name,May.sex,Peter.name,Peter.sex)    # 子类继承父类方法及属性
May.print_title()
Peter.print_title()

#输出
May female Peter male
woman
man

class Person(object):
    pass
class Child(Person):                 # Child 继承 Person
    pass
May = Child()
Peter = Person()    
print(isinstance(May,Child))         # True
print(isinstance(May,Person))        # True
print(isinstance(Peter,Child))       # False
print(isinstance(Peter,Person))      # True
print(issubclass(Child,Person))      # True

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
    def print_title(self):
        if self.sex == "male":
            print("man")
        elif self.sex == "female":
            print("woman")
class Child(Person):                # Child 继承 Person
    def print_title(self):
        if self.sex == "male":
            print("boy")
        elif self.sex == "female":
            print("girl")
May = Child("May","female")
Peter = Person("Peter","male")
print(May.name,May.sex,Peter.name,Peter.sex)
May.print_title()
Peter.print_title()

对扩展开放（Open for extension）：允许子类重写方法函数
对修改封闭（Closed for modification）：不重写，直接继承父类方法函数

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
class Child(Person):                          # Child 继承 Person
    def __init__(self,name,sex,mother,father):
        Person.__init__(self,name,sex)        # 子类对父类的构造方法的调用
        self.mother = mother
        self.father = father
May = Child("May","female","April","June")
print(May.name,May.sex,May.mother,May.father)   

class Person(object):
    def __init__(self,name,sex):
        self.name = name
        self.sex = sex
    def print_title(self):
        if self.sex == "male":
            print("man")
        elif self.sex == "female":
            print("woman")
class Child(Person):
    pass
class Baby(Child):
    pass
May = Baby("May","female")        # 继承上上层父类的属性
print(May.name,May.sex)         # May female
May.print_title()                 #woman 可使用上上层父类的方法

class Child(Person):
    def print_title(self):
        if self.sex == "male":
            print("boy")
        elif self.sex == "female":
            print("girl")
class Baby(Child):
    pass
May = Baby("May","female")
May.print_title()                # girl 优先使用上层类的方法

# 字符串，列表，元祖，字典，集合等等，都是可迭代对象
for i in [1, 2, 3]:
    print(i)
obj = {"a": 123, "b": 456}
for k in obj:
    print(k)

class foo(object):
	def __iter__(self):
		return 迭代器对象(生成器对象)
obj = foo() #obj是可迭代对象

#创建迭代器
class IT(object):
	def __init__(self):
		self.counter = 0
	def __iter__(self):
		return self
	def __next__(self):
		self.counter += 1
		if self.counter == 3:
			raise StopIteration()
#创建可迭代器对象
class foo(object):
	def __iter__(self):
		return IT()
obj = foo() #obj是可迭代对象
for item in obj:   #循环可迭代对象时,内部先执行obj.__iter__()并获取迭代器对象,然后再不断的执行迭代器对象的__next__方法
	print(item)

# 方法1: iter()将可迭代对象转换为迭代器
list=[1, 2, 3, 4]
it = iter(list)    # 创建迭代器对象
#使用next()遍历数据
print (next(it))  #1
print (next(it))  #2
#使用for循环遍历数据,for循环由于简洁,更常用
#for循环会执行迭代器的iter并获得返回的对象,一直反复的去执行next(对象)
for x in it:
    print (x, end=" ")   # 3 4
print (next(it))   #StopIteration
# 方法2: 创建一个迭代器
class MyNumbers:
  def __iter__(self):
    self.a = 1
    return self
  def __next__(self):
    if self.a <= 20:
      x = self.a
      self.a += 1
      return x
    else:
      raise StopIteration
#通过iter()和next()访问 
myclass = MyNumbers()
myiter = iter(myclass)
print(next(myiter))
print(next(myiter))
print(next(myiter))
for x in myiter:
  print(x)
print(next(myiter))

#创建了一个 num 生成器对象。显然，和普通函数不同，intNum() 函数的返回值用的是 yield 关键字，而不是 return 关键字，此类函数又成为生成器函数。
#创建生成器函数
def intNum():
    print("开始执行")
    for i in range(5):
        yield i
        print("继续执行")
#创建生成器对象num
num = intNum()
#调用 next() 内置函数
print(next(num))  #0
#调用 __next__() 方法
print(num.__next__())  #1
#通过for循环遍历生成器
for i in num:  #2 , 3, 4
    print(i)

num = intNum()
print(list(num))
num = intNum()
print(tuple(num)