面向对象——反射

Posted 2020-10-19 GraceZen

• 反射：通过字符串的形式操作对象相关的属性，python中一切皆对象（都可以使用反射）
• hasattr(object,name)：判断object中有没有一个name字符串对应的方法或属性
• getattr(object, name, default=None)
• 

  1 def getattr(object, name, default=None): # known special case of getattr
  2     """
  3     getattr(object, name[, default]) -> value
  4 
  5     Get a named attribute from an object; getattr(x, ‘y‘) is equivalent to x.y.
  6     When a default argument is given, it is returned when the attribute doesn‘t
  7     exist; without it, an exception is raised in that case.
  8     """
  9     pass

  View Code
• setattr(x, y, v)
• 

  1 def setattr(x, y, v): # real signature unknown; restored from __doc__
  2     """
  3     Sets the named attribute on the given object to the specified value.
  4 
  5     setattr(x, ‘y‘, v) is equivalent to ``x.y = v‘‘
  6     """
  7     pas

  View Code
• delattr(x, y)
• 

  1 def delattr(x, y): # real signature unknown; restored from __doc__
  2     """
  3     Deletes the named attribute from the given object.
  4 
  5     delattr(x, ‘y‘) is equivalent to ``del x.y‘‘
  6     """
  7     pass

  View Code

   

• 

   1 class People:
   2     country=‘China‘
   3 
   4     def __init__(self,name,age):
   5         self.name=name
   6         self.age=age
   7 
   8     def talk(self):
   9         print(‘%s is talking‘ %self.name)
  10 obj=People(‘egon‘,18)
  11 #通常情况下：
  12 # print(obj.name) #egon
  13 # print(obj.talk)#<bound method People.talk of <__main__.People object at 0x000000000287ACC0>>
  14 #
  15 # choice = input("==>:")##choice=‘name‘
  16 # print(object.choice)#object.‘name‘，报错
  17 #字符串映射
  18 
  19 #检测是否含有某属性
  20 # print(hasattr(obj,‘name‘)) #True
  21 # print(hasattr(obj,‘talk‘)) #True
  22 # print(hasattr(obj,‘run‘))#False
  23 
  24 #获取属性
  25 # print(getattr(obj,‘name‘))#egon
  26 # print(getattr(obj,‘run‘))#报错
  27 # print(getattr(obj,‘run‘,None))#None
  28 # fun = getattr(obj,‘talk‘)
  29 # fun()#egon is talking
  30 
  31 #设置属性
  32 setattr(obj,‘sex‘,‘male‘)  #obj.sex = male
  33 print(obj.sex)#male
  34 setattr(obj,‘show_name‘,lambda self : self.name+‘_s‘)#设置方法
  35 print(obj.show_name(obj))#egon_s
  36 print(obj.__dict__)
  37 #{‘name‘: ‘egon‘, ‘age‘: 18, ‘sex‘: ‘male‘, ‘show_name‘: <function <lambda> at 0x0000000001CF2E18>}
  38 
  39 #删除属性
  40 delattr(obj,‘age‘)
  41 delattr(obj,‘show_name‘)
  42 print(obj.__dict__)#{‘name‘: ‘egon‘, ‘sex‘: ‘male‘}
  43 delattr(obj,‘age‘)#不存在，则报错

  用法示例

   

  

  class Foo:
      staticField = ‘old boy‘
      def __init__(self):
          self.name = ‘wupeiqi‘
      @classmethod
      def func(self):
          return ‘func‘
      @staticmethod
      def bar():
          return ‘bar‘
  print(getattr(Foo,‘staticField‘))#old boy
  print(getattr(Foo,‘func‘))#<bound method Foo.func of <class ‘__main__.Foo‘>>
  print(getattr(Foo,‘bar‘))#<function Foo.bar at 0x0000000001E84510>

  用法示例——类也是对象