关于python 2.7:未引发python3抽象类typeerror

Python3 abstract class TypeError not raised

我在运行python 2.7、3.4和3.5。只有2.7使用以下代码引发类型错误。我想知道我是否做错了什么，这是一个已知的错误还是其他的错误？

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from abc import ABCMeta, abstractmethod

class Base(object):
__metaclass__ = ABCMeta

@abstractmethod
def bar(self):
pass

class Concrete(Base):
pass

confused = Concrete()

在Python2.7中，我得到了以下(有用的)错误：

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Traceback (most recent call last):
File"confused.py", line 16, in <module>
confused = Concrete()
TypeError: Can't instantiate abstract class Concrete with abstract methods bar

但是在python3.x中，它运行时没有错误(错误)。谢谢。

它们在python2.x和python3.x中表现不同。

Python 3.6

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# importing abstract base classes module
import abc

class GetterSetter(abc.ABC):
'''
ABSTRACT BASE CLASSES:

- An abstract base class is a kind of 'model' for other classes to be defined.
- It is not designed to construct instances, but can be subclassed by regular classes

- Abstract classes can define interface, or methods that must be implemented by its subclasses.

'''

# Abstract classes are not designed to be instantiated, only to be subclassed

# decorator for abstract class
@abc.abstractmethod
def set_val(self, input):
"""set the value in the instance"""
return

@abc.abstractmethod
def get_val(self):
"""Get and return a value from the instance..."""
return

# Inheriting from the above abstract class
class MyClass(GetterSetter):

# methods overriding in the GetterSetter
def set_val(self, input):
self.val = input

def get_val(self):
return self.val

# Instantiate
x = MyClass()
print(x) # prints the instance <__main__.MyClass object at 0x10218ee48>
x = GetterSetter() #throws error, abstract classes can't be instantiated

Python 2.x

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import abc

class GetterSetter(object):
# meta class is used to define other classes
__metaclass__ = abc.ABCMeta

# decorator for abstract class
@abc.abstractmethod
def set_val(self, input):
"""set the value in the instance"""
return

@abc.abstractmethod
def get_val(self):
"""Get and return a value from the instance..."""
return

# Inheriting from the above abstract class
class MyClass(GetterSetter):

# methods overriding in the GetterSetter
def set_val(self, input):
self.val = input

def get_val(self):
return self.val

# Instantiate
x = GetterSetter()
print(x)
x = GetterSetter() #throws error, abstract classes can't be instantiated

在这里检查我的答案。

声明在python3中更改的抽象基类为：

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import abc

class Base(metaclass=abc.ABCMeta):

@abc.abstractmethod
def bar(self):
pass

class Concrete(Base):
pass

Concrete() # Will raise a TypeError