@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
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#!/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
>
>
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
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)
# 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
>
>
Process finished with exit code 0
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
conn.from_conf("obj test")
AttributeError: 'MySQL' object has no attribute 'from_conf'
Process finished with exit code 1
