面向对象式编程

#函数式编程：

def fetch(host, username, password, sql):
pass
def create(host, username, password, sql):
pass
def remove(host, username, password, sql):
pass
def modify(host, username, password, sql):
pass
...
fetch(...)

#面向对象编程

class SQLHelper:

def fetch(self, sql):
pass
def create(self, sql):
pass
def remove(self, sql):
pass
def modify(self, sql):
pass

obj = SQLHelper()
obj.hhost = 'c1.salt.com'
obj.uusername = 'alex'
obj.pwd = "123"

obj.fetch("select * from A")

#__init__(self) 构造方法

#面向对象编程

class SQLHelper:

def __init__(self, a1, a2, a3)

self.hhost = a1
self.uusername = a2
self.pwd = a3

def fetch(self, sql):
pass
def create(self, sql):
pass
def remove(self, sql):
pass
def modify(self, sql):
pass

obj = SQLHelper('c1.salt.com','alex','123')
obj.fetch("select * from A")
~

#类的引用

class c1:
def __init__(self, name, obj):
self.name = name
self.obj = obj

class c2:
def __init__(self, name, age):
self.name = name
self.age = age

def show(self):
print(self.name)

c2_obj = c2('aa',11)
c1_obj = c1('alex', c2_obj) #c1类传入了c2_obj

print(c1_obj.obj.age)

“封装，继承，多态”

#继承

class F1: #父类，基类
def show(self):
print('show')

def foo(self):
print(self.name)

class F2(F1): #子类，派生类
def __init__(self, name):
self.name = name

def bar(self):
print('bar')

def show(self):
print ('F2.show')

obj = F2('alex')

obj.foo()