确定__getattr__是方法调用还是属性调用 [英] Determine if __getattr__ is method or attribute call

问题描述

有什么方法可以确定使用__getattr__的方法和属性调用之间的区别吗?

Is there any way to determine the difference between a method and an attribute call using __getattr__?

即在:

class Bar(object):
    def __getattr__(self, name):
        if THIS_IS_A_METHOD_CALL:
            # Handle method call
            def method(**kwargs):
                return 'foo'
            return method
        else:
            # Handle attribute call
            return 'bar'

foo=Bar()
print(foo.test_method()) # foo
print(foo.test_attribute) # bar

这些方法不是本地的，因此无法使用getattr/callable确定它.我也理解方法是属性，并且可能没有解决方案.只是希望有一个.

The methods are not local so it's not possible to determine it using getattr/callable. I also understand that methods are attributes, and that there might not be a solution. Just hoping there is one.

推荐答案

您根本无法确定在__getattr__挂钩中将如何使用对象.例如，您可以在不调用方法的情况下访问方法，将它们存储在变量中，然后稍后对其进行调用.

You cannot tell how an object is going to used in the __getattr__ hook, at all. You can access methods without calling them, store them in a variable, and later call them, for example.

使用__call__方法返回对象，该对象将在调用时被调用:

Return an object with a __call__ method, it'll be invoked when called:

class CallableValue(object):
    def __init__(self, name):
        self.name = name
    def __call__(self, *args, **kwargs):
        print "Lo, {} was called!".format(self.name)

class Bar(object):
    def __getattr__(self, name):
        return CallableValue(name)

但是此实例与字符串或列表不同.

but instances of this will not be the same thing as a string or a list at the same time.

演示:

>>> class CallableValue(object):
...     def __init__(self, name):
...         self.name = name
...     def __call__(self, *args, **kwargs):
...         print "Lo, {} was called!".format(self.name)
... 
>>> class Bar(object):
...     def __getattr__(self, name):
...         return CallableValue(name)
... 
>>> b = Bar()
>>> something = b.test_method
>>> something
<__main__.CallableValue object at 0x10ac3c290>
>>> something()
Lo, test_method was called!

这篇关于确定__getattr__是方法调用还是属性调用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！