Python集（）.IsubSet（）未按预期工作

我试图使用

set（）.issubset（）

来比较序列。正如你所能想象的，它没有按预期工作；）预告：抱歉，代码太长了

class T(object):
  def __init__(self, value, attributes = None):
    self.value = value
    self.attributes = Attributes(attributes)

  def __eq__(self, other):
    if not isinstance(other, T):
      return False
    if self.value == other.value and self.attributes == other.attributes:
      return True
    else:
      return False

  def __ne__(self, other):
    if not isinstance(other, T):
      return True
    if self.value != other.value or self.attributes != other.attributes:
      return True
    else:
      return False

class Attributes(dict):
  def __init__(self, attributes):
    super(dict, self)
    self.update(attributes or dict())

  def __eq__(self, other):
    if self.items() == other.items():
      return True
    else:
      return False

  def __ne__(self, other):
    if not self.items() == other.items():
      return True
    else:
      return False

  def __cmp__(self, other):
    return self.items().__cmp__(other.items())


x = [T("I", {'pos': 0}), T("am", {'pos': 1}), T("a", {'pos': 2}), T("test", {'pos': 3})]
y = [T("a", {'pos': 2}), T("test", {'pos': 3})] 
xx = set(x)
yy = set(y)

assert y[0] == x[2], "__eq__ did fail, really?" #works
assert y[1] == x[3], "__eq__ did fail, really?" #works
assert xx-(yy-xx) == xx, "set subtract not working" #works, but is nonsense. see accepted answer
assert not xx.issubset(yy), "i am doing it wrong..." #works
assert yy.issubset(xx), "issubset not working :(" #FAILS!

运行上述代码会导致最后一次断言失败：

$ python
Python 2.7.2 (v2.7.2:8527427914a2, Jun 11 2011, 15:22:34) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import issubsettest
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "issubsettest.py", line 52, in <module>
    assert yy.issubset(xx), "issubset not working :("
AssertionError: issubset not working :(
>>> 

$python
Python 2.7.2（v2.7.2:8527414a2，2011年6月11日，15:22:34）
[GCC 4.2.1（苹果公司建造5666）（dot 3）]关于达尔文
有关详细信息，请键入“帮助”、“版权”、“信用证”或“许可证”。
>>>进口签证
回溯（最近一次呼叫最后一次）：
文件“”，第1行，在
文件“issubsettest.py”，第52行，在
断言yy.issubset（xx），“issubset不工作：（”
AssertionError:issubset不工作：(
>>> 

---

我在这里遗漏了什么？

您的对象正在被其

id

散列（您没有覆盖

\uuuuuuhash\uuuuuu

）。当然，它们不是子集，因为

xx

和

yy

包含唯一的对象

为了做到这一点，您需要使用某种

\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu

函数

class T(object):
    #<snip> ...

    def __hash__(self):
        return hash(self.value)

    #... </snip>

---

这应该很明显为什么这是

真的

我认为这是因为用户我认为问题在于你的类

T

没有覆盖方法

\uuuuuuuhash\uuuuuu

，其实例在散列集合中不可用。我刚刚用Python 3.3测试了您的代码，它给出了错误：

TypeError:unhabable type:'T'

在

xx=set（x）行上

所以肯定是缺少

\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu

。然后解释他应该如何修复它。@JBernardo——修复它完全是另一回事。OP需要以某种方式覆盖

\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu…这有帮助吗？好的，我明白了，谢谢！让我困惑的是，
xx-（yy-xx）
似乎起到了一些作用。但我认为它所做的仅仅是
yy-set（）
括号内和
xx-set（）
之后。事后看来，这个断言甚至是完全错误的。我认为我无法通过减法证明任何东西。@mgilson是的！谢谢你的解释！
xx - set([]) == xx