python 一切都大于无吗？

Is everything greater than None?

提问by Attila O.

Is there a Python built-in datatype, besides None, for which:

除了None，是否有 Python 内置数据类型，为此：

>>> not foo > None
True

where foois a value of that type? How about Python 3?

foo该类型的值在哪里？Python 3 怎么样？

回答by John Feminella

Noneis always less than any datatype in Python 2 (see object.c).

None始终小于 Python 2 中的任何数据类型（请参阅 参考资料object.c）。

In Python 3, this was changed; now doing comparisons on things without a sensible natural ordering results in a TypeError. From the 3.0 "what's new" updates:

在 Python 3 中，这被改变了；现在对没有合理自然排序的事物进行比较会导致TypeError. 从3.0“新功能”更新开始：

Python 3.0 has simplified the rules for ordering comparisons:

The ordering comparison operators (<, <=, >=, >) raise a TypeErrorexception when the operands don't have a meaningful natural ordering. Thus, expressions like: 1 < '', 0 > Noneor len <= lenare no longer valid, and e.g. None < Noneraises TypeErrorinstead of returning False. A corollary is that sorting a heterogeneous list no longer makes sense – all the elements must be comparable to each other. Note that this does not apply to the ==and !=operators: objects of different incomparable types always compare unequal to each other.

Python 3.0 简化了排序比较的规则：

当操作数没有有意义的自然排序时，排序比较运算符 ( <, <=, >=, >) 会引发TypeError异常。因此，像: 1 < '', 0 > Noneor这样的表达式len <= len不再有效，例如None < NoneraisesTypeError而不是 return False。一个推论是对异构列表进行排序不再有意义——所有元素必须相互比较。请注意，这不适用于==and!=运算符：不同不可比较类型的对象总是相互比较不相等。

This upset some people since it was often handy to do things like sort a list that had some Nonevalues in it, and have the Nonevalues appear clustered together at the beginning or end. There was a thread on the mailing list about thisa while back, but the ultimate point is that Python 3 tries to avoid making arbitrary decisions about ordering (which is what happened a lot in Python 2).

这让一些人感到不安，因为这样做通常很方便，例如对包含一些None值的列表进行排序，并让这些None值在开头或结尾聚集在一起。不久前，邮件列表上有一个关于此的主题，但最终的一点是 Python 3 试图避免对排序做出任意决定（这在 Python 2 中经常发生）。

回答by Torsten Marek

From the Python 2.7.5source (object.c):

来自 Python 2.7.5源代码 ( object.c)：

static int
default_3way_compare(PyObject *v, PyObject *w)
{
    ...
    /* None is smaller than anything */
    if (v == Py_None)
            return -1;
    if (w == Py_None)
            return 1;
    ...
}

EDIT: Added version number.

编辑：添加了版本号。