Use hasattr (), getattr (), setattr () function

1. hasattr(object, name)

　　The name attribute is determined whether there is a target object, of course, for the python objects, properties and methods comprising a variable; the returns True, False if no; Note that the parameter is a string type name, it is determined whether the variable is to The method, which names as strings mass participation; getattr and also setattr;

>>> 
>>> class A():
    name = 'python'
    def func(self):
        return 'A()类的方法func()'

    
>>> 
>>> hasattr(A, 'name')
True
>>> 
>>> hasattr(A, 'age')
False
>>> 
>>> hasattr(A, 'func')
True
>>> 

　　2. getattr(object, name[, default])

　　Value acquisition target object attribute, the attribute value is returned if present, is not present if the two cases, one is no default parameter directly error; given default parameters, if the object does not have a name attribute, then returns given default value; if the given property name is the method of the object, the return is a function of the object, call the function object to obtain the function return value; call word is after the function objects parentheses, such as func is to the func ();

　　Also note that if the method given FUNC () is an example of a function, then the write getattr (A, 'func') (), as fun () is an example of a function, it can not be called with A class object, should be written getattr (a (), 'func') (); class distinction instance function and a function of what can be simply understood, the function definition instance, direct def func (self) :, then the definition is the only class instantiated, using the instantiation object class to invoke; while class function definition, @classmethod need to decorate, default parameter function generally CLS, class function may be called directly by the class object, without the need for classes examples of;

>>> 
>>> class A():
    name = 'python'
    def func(self):
        return 'Hello world'

    
>>> 
>>> getattr(A, 'name')
'python'
>>> 
>>> getattr(A, 'age')　　　　# age变量不存在则报错

Traceback (most recent call last):
  File "<pyshell#464>", line 1, in <module>
    getattr(A, 'age')
AttributeError: class A has no attribute 'age'
>>> 
>>> getattr(A, 'age', 20)
20
>>> 
>>> getattr(A, 'func')
<unbound method A.func>
>>>
    getattr (A, 'FUNC') ()
Traceback (MOST Recent Last Call):
function can not be called an object class A, the error>>> getattr (A, 'func'

  File "<470 pyshell #>", Line. 1, in <Module1 >
TypeError: unbound method func() must be called with A instance as first argument (got nothing instead)
>>> 
>>> getattr(A(), 'func')()
'Hello world'
>>> 

>>> class A(object):
　　　　name = 'python'
　　　　@classmethod
　　　　def func(cls):
　　　　　　return 'the method of A object.'

>>> 
>>> getattr(A, 'func')()
'the method of A object.'
>>>

　　3. setattr(object, name, value)

　　Assigned to the name attribute value object object, if the object was originally given attribute name exists, it will change setattr property is given value; if the object had attribute name does not exist, setattr property created in the object, and assign for a given value;

>>> 
>>> class A():
    name = 'python'
    def func(self):
        return 'Hello world'

    
>>> 
>>> setattr(A, 'name', 'java')
>>> getattr(A, 'name')
'java'
>>> 
>>> setattr(A, 'age', 20)
>>> getattr(A, 'age')
20
>>> 

 

 

　　First determines whether there is a general property of objects, if present, is returned; if not, then add attributes to the object and assignment; if-else simple determination:

>>> 
>>> class A():
    name = 'python'
    def func(self):
        return 'Hello world'

    
>>> 
>>> if hasattr(A, 'age'):
    print getattr(A, 'age')
else:
    setattr(A, 'age', 20)

    
>>> 
>>> getattr(A, 'age')
20
>>> 

高级使用

# - * - Coding: UTF-. 8 - * - Import SYS
 Import Platform class InfoCollection ( Object ): DEF the collect ( Self ): # collecting platform information # first determines the current platform, depending on the platform to perform different methods the try : FUNC = getattr ( Self , Platform . System () . Lower ()) info_data = FUNC () formatted_data = Self . build_report_data ( info_data ) return




formatted_data except AttributeError: sys.exit("不支持当前操作系统： [%s]! " % platform.system()) @staticmethod def linux(): from plugins.collect_linux_info import collect return collect() @staticmethod def windows(): from plugins.collect_windows_info import Win32Info return Win32Info().collect() @staticmethod DEF build_report_data ( Data ): # a left interface to facilitate data after filtering functions or increases Pass return Data