getattr()函数是Python自省的核心函数,具体使用大体如下:
获取对象引用getattr
class A: def __init__(self): self.name = 'zhangjing' #self.age='' def method(self): print"method print" Instance = A() print getattr(Instance,'name,'not find') #如果Instance 对象中有属性name则打印self.name的值,否则打印'not find' print getattr(Instance,'age','not find') #如果Instance 对象中有属性age则打印self.age的值,否则打印'not find' print getattr(a,'method','default') #如果有方法method,否则打印其地址,否则打印default print getattr(a,'default')() #如果有方法method,运行函数并打印None否则打印default
注:使用getattr可以轻松实现工厂模式。
例:一个模块支持html、text、xml等格式的打印,根据传入的formate参数的不同,调用不同的函数实现几种格式的输出
import statsout def output(data,format="text"): output_function = getattr(statsout,"output_%s" % format) return output_function(data) setattr(object,name,value) This is the counterpart of getattr(). The arguments are an object,a string and an arbitrary value. The string may name an existing attribute or a new attribute. The function assigns the value to the attribute,provided the object allows it. For example,setattr(x,'foobar',123) is equivalent to x.foobar = 123.
这是相对应的getattr()。参数是一个对象,一个字符串和一个任意值。字符串可能会列出一个现有的属性或一个新的属性。这个函数将值赋给属性的。该对象允许它提供。例如,“foobar”,123)相当于x.foobar = 123。
delattr(object,name)
This is a relative of setattr(). The arguments are
an object and a string. The string must be the name of one of the object's
attributes. The function deletes the named attribute,provided the object allows
it. For example,delattr(x,'foobar') is
equivalent to del x.foobar.
与setattr()相关的一组函数。参数是由一个对象(记住python中一切皆是对象)和一个字符串组成的。string参数必须是对象属性名之一。该函数删除该obj的一个由string指定的属性。delattr(x,'foobar')=del x.foobar
语法:
hasattr(object,name) -> bool
>>> li=["zhangjing","zhangwei"] >>> getattr(li,"pop") <built-in method pop of list object at 0x011DF6C0> >>> li.pop <built-in method pop of list object at 0x011DF6C0> >>> li.pop() 'zhangwei' >>> getattr(li,"pop")() 'zhangjing' >>>getattr(li,"append")("Moe")