[英]How can I use `str.format` directly as `__repr__`?
Say I want to debug a simple class with an attribute myattribute
. 假设我想调试一个带有属性myattribute
的简单类。 I create a repr
method like this: 我创建一个这样的repr
方法:
class SimpleClass:
def __repr__(self):
return "{0.myattribute}".format(self)
It feels a bit redundant, so I would prefer to use format
directly: 感觉有点多余,所以我更喜欢直接使用format
:
class SimpleClass:
__repr__ = "{0.myattribute}".format
...but that fails with an IndexError: tuple index out of range
. ...但是因为IndexError: tuple index out of range
而失败。 I understand it that format
cannot access the self
argument, but I do not see why. 我理解format
无法访问self
参数,但我不明白为什么。
Am I doing something wrong, is this a CPython limitation – or what else? 我做错了什么,这是CPython限制 - 或者还有什么?
"{0.myattribute}".format
is already a bound method on the string object ( "{0.myattribute}"
). "{0.myattribute}".format
已经是字符串对象( "{0.myattribute}"
)的绑定方法。 So when the calling code attempts to look up, say, x.__repr__
(where x
is a SimpleClass
instance), Python finds the __repr__
attribute of SimpleClass
, but then cannot recognize it as a SimpleClass
method - the descriptor protocol is not honoured (the string method has no __get__
attribute). 因此,当调用代码试图查找时,例如x.__repr__
(其中x
是SimpleClass
实例),Python找到SimpleClass
的__repr__
属性,但是后来无法将其识别为SimpleClass
方法 - 描述符协议不受尊重( string方法没有__get__
属性)。
It appears that in 3.4, using a lambda
will work, although I could have sworn it had to be a real function in previous versions. 似乎在3.4中,使用lambda
会起作用,虽然我可以发誓它必须是以前版本中的真正功能。 functools.partial
will not work. functools.partial
不起作用。 But you really should be using a real function anyway. 但无论如何你真的应该使用真正的功能。 Sorry it's not as DRY as you'd like. 对不起它不像你想的那么干。
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