__getattr__和getattr之间是什么关系? [英] What is the relationship between __getattr__ and getattr?

问题描述

我知道这段代码是正确的:

I know this code is right:

class A:   
    def __init__(self):
        self.a = 'a'  
    def method(self):   
        print "method print"  

a = A()   
print getattr(a, 'a', 'default')   
print getattr(a, 'b', 'default')  
print getattr(a, 'method', 'default') 
getattr(a, 'method', 'default')()   

这是错误的:

# will __getattr__ affect the getattr?

class a(object):
    def __getattr__(self,name):
        return 'xxx'

print getattr(a)

这也是错误的:

a={'aa':'aaaa'}
print getattr(a,'aa')

我们应该在哪里使用__getattr__和getattr?

Where should we use __getattr__ and getattr?

推荐答案

Alex的回答很好，但是自从您提出要求以来，它为您提供了示例代码:)

Alex's answer was good, but providing you with a sample code since you asked for it :)

class foo:
    def __init__(self):
        self.a = "a"
    def __getattr__(self, attribute):
        return "You asked for %s, but I'm giving you default" % attribute


>>> bar = foo()
>>> bar.a
'a'
>>> bar.b
"You asked for b, but I'm giving you default"
>>> getattr(bar, "a")
'a'
>>> getattr(bar, "b")
"You asked for b, but I'm giving you default"

总之，答案是

您使用

__getattr__来定义如何处理未找到

和

getattr以获取 属性

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