动态属性和对象

1 getattr



In [39]:

    
class Print(object):
    class_name = 'print'
    def __init__(self):
        self.object_name='object'
    def do_foo(self):
        print 'foo'
    def do_bar(self):
        return 'bar'
    def do_two(self, value):
        print value
    @property
    def names(self):
        return self.object_name
    @classmethod
    def class_bar(cls):
        print 'class_bar'
    @staticmethod
    def static_foo():
        print 'static_foo'

1.1class attribute



In [40]:

    
print getattr(Print, 'class_name')









    



print

1.2 object attribute



In [41]:

    
obj = Print()
print getattr(obj, 'object_name')









    



object



In [21]:

    
# if the attribute does not exist
print getattr(obj, 'my_name')









    



---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-21-f82a56842dc1> in <module>()
      1 # if the attribute does not exist
----> 2 print getattr(obj, 'my_name')

AttributeError: 'Print' object has no attribute 'my_name'



In [42]:

    
# if not exist, give a default value
print getattr(obj, 'my_name', 'default_value')









    



default_value

1.3 object function

By calling getattr function, you will get the function object



In [43]:

    
getattr(obj, 'do_foo')()

foo



In [44]:

    
print getattr(obj, 'do_bar')()

bar



In [45]:

    
getattr(obj, 'do_two')('gaufung')









    



gaufung



In [46]:

    
getattr(obj, 'names')









    Out[46]:





'object'

1.4 class method and static method



In [16]:

    
getattr(obj, 'class_bar')()









    



class_bar



In [17]:

    
getattr(obj, 'static_foo')()









    



static_foo

2 hasattr



In [28]:

    
hasattr(obj, 'do_bar')









    Out[28]:





True



In [29]:

    
hasattr(obj, 'gaofeng')









    Out[29]:





False

3 setattr



In [33]:

    
setattr(obj, 'name', 'gaufung')
print hasattr(obj, 'name')
print getattr(obj, 'name')









    



True
gaufung



In [34]:

    
def add(x, y):
    return x+y

setattr(obj, 'add', add)
print getattr(obj, 'add')(2,1)

4 delattr



In [36]:

    
print hasattr(obj, 'add')









    



True



In [37]:

    
delattr(obj, 'add')
print hasattr(obj, 'add')









    



False

5 eval



In [38]:

    
func_name = 'add'
eval(func_name)(1,2)









    Out[38]:





3