本文翻译自:super() raises “TypeError: must be type, not classobj” for new-style class
The following use of super()
raises a TypeError: why? 以下使用super()
会引发TypeError:为什么?
>>> from HTMLParser import HTMLParser
>>> class TextParser(HTMLParser):
... def __init__(self):
... super(TextParser, self).__init__()
... self.all_data = []
...
>>> TextParser()
(...)
TypeError: must be type, not classobj
There is a similar question on StackOverflow: Python super() raises TypeError , where the error is explained by the fact that the user class is not a new-style class. StackOverflow上有一个类似的问题: Python super()引发TypeError ,其中错误的解释是用户类不是新式类。 However, the class above is a new-style class, as it inherits from object
: 但是,上面的类是一个新式类,因为它继承自object
:
>>> isinstance(HTMLParser(), object)
True
What am I missing? 我错过了什么? How can I use super()
, here? 我怎么能在这里使用super()
?
Using HTMLParser.__init__(self)
instead of super(TextParser, self).__init__()
would work, but I would like to understand the TypeError. 使用HTMLParser.__init__(self)
而不是super(TextParser, self).__init__()
可以工作,但我想了解TypeError。
PS: Joachim pointed out that being a new-style-class instance is not equivalent to being an object
. PS:Joachim指出,作为一个新式的实例并不等同于成为一个object
。 I read the opposite many times, hence my confusion (example of new-style class instance test based on object
instance test: https://stackoverflow.com/revisions/2655651/3 ). 我多次反复阅读,因此我的困惑(基于object
实例测试的新式类实例测试示例: https : //stackoverflow.com/revisions/2655651/3 )。
#1楼
参考:https://stackoom.com/question/eh3G/对于新式类-super-引发-TypeError-必须是type-而不是classobj
#2楼
You can also use class TextParser(HTMLParser, object):
. 您还可以使用class TextParser(HTMLParser, object):
This makes TextParser
a new-style class, and super()
can be used. 这使得TextParser
成为一种新式的类,并且可以使用super()
。
#3楼
the correct way to do will be as following in the old-style classes which doesn't inherit from 'object' 正确的方法是在旧式类中继承“对象”
class A:
def foo(self):
return "Hi there"
class B(A):
def foo(self, name):
return A.foo(self) + name
#4楼
The problem is that super
needs an object
as an ancestor: 问题是super
需要一个object
作为祖先:
>>> class oldstyle:
... def __init__(self): self.os = True
>>> class myclass(oldstyle):
... def __init__(self): super(myclass, self).__init__()
>>> myclass()
TypeError: must be type, not classobj
On closer examination one finds: 仔细研究后发现:
>>> type(myclass)
classobj
But: 但:
>>> class newstyle(object): pass
>>> type(newstyle)
type
So the solution to your problem would be to inherit from object as well as from HTMLParser. 因此,您的问题的解决方案是从对象以及HTMLParser继承。 But make sure object comes last in the classes MRO: 但要确保对象在MRO类中排在最后:
>>> class myclass(oldstyle, object):
... def __init__(self): super(myclass, self).__init__()
>>> myclass().os
True
#5楼
FWIW and though I'm no Python guru I got by with this FWIW虽然我不是Python大师,但我还是接受了这个
>>> class TextParser(HTMLParser):
... def handle_starttag(self, tag, attrs):
... if tag == "b":
... self.all_data.append("bold")
... else:
... self.all_data.append("other")
...
...
>>> p = TextParser()
>>> p.all_data = []
>>> p.feed(text)
>>> print p.all_data
(...)
Just got me the parse results back as needed. 刚刚根据需要解析了解析结果。
#6楼
If you look at the inheritance tree (in version 2.6), HTMLParser
inherits from SGMLParser
which inherits from ParserBase
which doesn't inherits from object
. 如果查看继承树(在2.6版本中), HTMLParser
继承自从ParserBase
继承的SGMLParser
,它不从object
继承。 Ie HTMLParser is an old-style class. 即HTMLParser是一个旧式的类。
About your checking with isinstance
, I did a quick test in ipython: 关于你的isinstance
,我在ipython中做了一个快速测试:
In [1]: class A: ...: pass ...: In [2]: isinstance(A, object) Out[2]: True
Even if a class is old-style class, it's still an instance of object
. 即使一个类是旧式类,它仍然是一个object
的实例。