python基础第十八课--OOP简化数据结构初始化过程（小白piao分享）

在python编程的过程中经常会碰到需要编写很多的类，调用很多次__init__()方法。这样经常是的代码重复量非常之大。

有没有办法可以简化构造初始化的个数，减少代码量？当然可以！方法就是将所有的属性初始化赋值放在一个基类中完成。代码如下：

1、对一般参数：

class Struct:
    _field = []
    def __init__(self,*args):
        if len(args) != len(self._field):
            raise TypeError('please insert {} arguments,but {} were given'.format(len(self._field),len(args)))
        else:
            for name, value in zip(self._field,args):
                setattr(self,name,value)

import math
class Stock(Struct):
    _field = ['name','shares','price']
class Point(Struct):
    _field = ['x','y']
class Circle(Struct):
    _field = ['radius']
    @property
    def area(self):
        return math.pi * self.radius ** 2

c = Circle(4.0)#此处会调用父类的构造函数
print(c.area)

2、添加关键字参数：

2.1 让关键字参数作为映射，只允许关键字参数名字是_fields中已有的参数名。

代码如下：

class Struct:
    _field = []
    def __init__(self,*args,**kwargs):
        if len(args) > len(self._field):
            raise TypeError('please insert {} arguments,but {} were given'.format(len(self._field),len(args)))
        else:
            for name, value in zip(self._field,args):
                setattr(self,name,value)
            for name in self._field[len(args) : ]:
                setattr(self,name,kwargs.pop(name))#pop返回该键所对应的值，并将其从关键字表（kwargs）中删除；设置在底层字典中
                #如果不存在该名称的键，会报错，而该名称必须是_field中有的名称
        if kwargs:
            raise TypeError('Invalid argument:{}'.format(','.join(kwargs)))

class Stock(Struct):
    _field = ['name','share','price']
    def prt(self):
        print(self.name,self.share,self.price)

#此时，关键字参数只能选择列表中有的参数
s = Stock('小白piao',share = '1000',price = '999')
s.prt()#小白piao 1000 999
s = Stock('小白piao',share = '1000',hehe = '999')#hehe不存在
'''
Traceback (most recent call last):
  File "F:/PycharmProjects/class_obj/class_one.py", line 317, in <module>
    s = Stock('小白piao',share = '1000',呵呵 = '999')
  File "F:/PycharmProjects/class_obj/class_one.py", line 306, in __init__
    setattr(self,name,kwargs.pop(name))#pop返回该键所对应的值，并将其从关键字表（kwargs）中删除；设置在底层字典中
KeyError: 'price'
'''

2.2 想要添加不存在的关键字参数：

代码如下：

class Struct:
    _field = []
    def __init__(self,*args,**kwargs):
        if len(args) != len(self._field):
            raise TypeError('please insert {} arguments,but {} were given'.format(len(self._field),len(args)))

        for name, value in zip(self._field,args):
            setattr(self,name,value)
        extra_args = kwargs.keys() - self._field
        for name in extra_args:
            setattr(self,name,kwargs.pop(name))
        if kwargs:
            raise TypeError('Duplicate values for {}'.format(','.join(kwargs)))

class Stock(Struct):
    _field = ['name','share','price']
    def prt(self):
        print(self.__dict__)

sto = Stock('小白piao',100,99,hehe = '你是菜鸡！')
sto.prt()#{'name': '小白piao', 'share': 100, 'price': 99, 'hehe': '你是菜鸡！'}