綁定方法與非綁定方法

1.綁定方法

1.1綁定到類的方法:@classmethod裝飾器裝飾的方法

@classmethod是給類使用的，即綁定到類，
1.類在調用該方法時，會將類本身當做參數傳給類方法的第一個參數(即self)
2.對象在調用該方法時，也會將類本身當做參數傳給類方法的第一個參數(即self)
3.哪個類調用，就傳入哪個類，子類在調用父類中的類綁定方法時，傳入的是子類

#!/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)
#對象也可以調用，但是默認傳的第一個參數仍然是類
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
# 哪個類調用，傳入的就是哪個類的。這里傳入的是子類mysql的類
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綁定到對象的方法:沒有被任何裝飾器裝飾的方法

#!/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)
    # 綁定到對象的方法
    def from_obj(cls):
        print(cls)
obj = MySQL("","")
print(obj.from_conf)
# 綁定到對象的方法
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.非綁定方法

在類內部使用staticmethod裝飾的函數即是非綁定方法，就是普通函數
staticmethod不與類或對象綁定，誰都可以調用，沒有自動傳值的效果

#!/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

"非綁定方法也可以是隱藏函數，同樣是不能被外部調用"
#!/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")

# "兩條語句報錯都是下面的錯誤，可以自行嘗試"
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