绑定方法与非绑定方法

1.绑定方法

1.1绑定到类的方法:@classmethod装饰器装饰的方法

@classmethod是给类使用的，即绑定到类，
1.类在调用该方法时，会将类本身当做参数传给类方法的第一个参数(即self)
2.对象在调用该方法时，也会将类本身当做参数传给类方法的第一个参数(即self)
3.哪个类调用，就传入哪个类，子类在调用父类中的类绑定方法时，传入的是子类

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita

class MySQL:
    def __init__(self,host,port):
        self.host=host
        self.port=port

    @classmethod
    def from_conf(cls):
        print(cls)

conn=MySQL("127.0.0.1","3306")
print(MySQL.from_conf)
print(conn.from_conf)
#对象也可以调用，但是默认传的第一个参数仍然是类
MySQL.from_conf()
conn.from_conf()

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
<bound method MySQL.from_conf of <class '__main__.MySQL'>>
<bound method MySQL.from_conf of <class '__main__.MySQL'>>
<class '__main__.MySQL'>
<class '__main__.MySQL'>

Process finished with exit code 0

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita

class MySQL:
    def __init__(self,host,port):
        self.host=host
        self.port=port

    @classmethod
    def from_conf(cls):
        print(cls)

class mysql(MySQL):
    pass
# 哪个类调用，传入的就是哪个类的。这里传入的是子类mysql的类
mysql.from_conf()

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
<class '__main__.mysql'>

Process finished with exit code 0

1.2绑定到对象的方法:没有被任何装饰器装饰的方法

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita
class MySQL:
    def __init__(self,host,port):
        self.host=host
        self.port=port

    @classmethod
    def from_conf(cls):
        print(cls)
    # 绑定到对象的方法
    def from_obj(cls):
        print(cls)
obj = MySQL("","")
print(obj.from_conf)
# 绑定到对象的方法
print(obj.from_obj)

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
<bound method MySQL.from_conf of <class '__main__.MySQL'>>
<bound method MySQL.from_obj of <__main__.MySQL object at 0x0000027E6AD9EB00>>

Process finished with exit code 0

2.非绑定方法

在类内部使用staticmethod装饰的函数即是非绑定方法，就是普通函数
staticmethod不与类或对象绑定，谁都可以调用，没有自动传值的效果

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita

class MySQL:
    def __init__(self,host,port):
        self.host=host
        self.port=port

    @staticmethod
    def from_conf(cls):
        print(cls)
        #return cls("127.0.0.1","3306")

conn=MySQL("127.0.0.1","3306")

MySQL.from_conf("class test")
conn.from_conf("obj test")

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
class test
obj test

Process finished with exit code 0

"非绑定方法也可以是隐藏函数，同样是不能被外部调用"
#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: vita

class MySQL:
    def __init__(self,host,port):
        self.host=host
        self.port=port

    @staticmethod
    def __from_conf(cls):
        print(cls)
        #return cls("127.0.0.1","3306")

conn=MySQL("127.0.0.1","3306")

# "两条语句报错都是下面的错误，可以自行尝试"
MySQL.from_conf("class test")
conn.from_conf("obj test")

E:\PythonProject\python-test\venvP3\Scripts\python.exe E:/PythonProject/python-test/BasicGrammer/test.py
Traceback (most recent call last):
  File "E:/PythonProject/python-test/BasicGrammer/test.py", line 19, in <module>
    conn.from_conf("obj test")
AttributeError: 'MySQL' object has no attribute 'from_conf'

Process finished with exit code 1