python面向对象 反射原理解析

import time
class Date:
  def __init__(self,year,month,day):
    self.year=year
    self.month=month
    self.day=day
  # @staticmethod
  # def now():
  #   t=time.localtime()
  #   return Date(t.tm_year,t.tm_mon,t.tm_mday)
  @classmethod     #改成类方法
  def now(cls):
    t=time.localtime()
    return cls(t.tm_year,t.tm_mon,t.tm_mday) #哪个类来调用,即用哪个类cls来实例化
class EuroDate(Date):
  def __str__(self):
    return 'year:%s month:%s day:%s' %(self.year,self.month,self.day)
e=EuroDate.now()
print(e)        #我们想触发EuroDate.__str__,此时e就是由EuroDate产生的,结果如我们所愿
'''
输出结果:
year:2017 month:3 day:3
'''

class Foo:
  def __init__(self):
    self.name = 'egon'
    self.age = 51
  def func(self):
    print('hello')
egg = Foo()
print(hasattr(egg,'name'))   #先判断name在egg里面存在不存在，结果是True
print(getattr(egg,'name'))   #如果为True它才去得到，结果是egon
print(hasattr(egg,'func'))   #结果是True
print(getattr(egg,'func'))   #得到的是地址<bound method Foo.func of <__main__.Foo object at 0x0000000001DDA2E8>>
getattr(egg,'func')()    #在这里加括号才能得到，因为func是方法，结果是hello

一般用法如下，先判断是否hasattr，然后取getattr
if hasattr(egg,'func'):
  getattr(egg,'func')()  #结果是hello
else:
  print('没找到')

class Foo:
  f = 123
  @classmethod
  def class_method_dome(cls):
    print('class_method_dome')
  @staticmethod
  def static_method_dome():
    print('static_method_dome')    
print(hasattr(Foo,'class_method_dome'))     #结果是True
method = getattr(Foo,'class_method_dome')
method()                #结果是class_method_dome

print(hasattr(Foo,'static_method_dome'))     #结果是True
method1 = getattr(Foo,'static_method_dome')
method1()               #结果是static_method_dome

import mymodule
print(hasattr(mymodule,'test'))
getattr(mymodule,'test')()
p = getattr(mymodule,'test')
p()               #相当于上面getattr(mymodule,'test')()

def demo1():
  print('hello')
import sys
module_obj = sys.modules[__name__]    #相当于'__main__'
print(module_obj)         #结果是<module '__main__' from 'C:/Users/Administrator/Desktop/test.py'>
print(hasattr(module_obj,'demo1'))    #结果是True
getattr(module_obj,'demo1')()     #结果是hello

def 注册():
  print('regiester')
def 登录():
  print('login')
def 购物():
  pass
print('注册，登录，购物')
ret = input('请输入你要做的操作：')
import sys
my_module = sys.modules[__name__] #利用sys模块导入一个自己的模块
if hasattr(my_module,ret):
  getattr(my_module,ret)()