为什么整数在 python 2 中缺少一些特殊方法？
Why are integers missing some special methods in python 2?
在 python 2 或 3 中内置 类 有明确定义的特殊方法。 Explicit is better than implicit 和所有爵士乐。
5. > 4.
# True
(5.).__ge__(4.)
# True
但在 python2 中，某些方法存在例外情况，至少在整数方面是这样。
5 > 4
# True
(5).__ge__(4)
# AttributeError: 'int' object has no attribute '__ge__'
# But not all of them fail!
(5).__add__(4)
# 9
这种行为背后的原因是什么？为什么要这样设计？
我正在使用 Python 2.7.12
data model has been updated between python-2.x and python-3.x. In python-2.x one could use the __cmp__ method:
object.__cmp__(self, other)
Called by comparison operations if rich comparison (see above) is
not defined. Should return a negative integer if self < other,
zero if self == other, a positive integer if self > other. If no __cmp__(), __eq__() or __ne__() operation is defined,
class instances are compared by object identity ("address"). See
also the description of __hash__() for some important notes on
creating hashable objects which support custom comparison operations
and are usable as dictionary keys. (Note: the restriction that
exceptions are not propagated by __cmp__() has been removed since
Python 1.5.)
（已添加格式）
rich comparison 运算符是 __le__, __ge__, etc.. So in python-2.x 还有一个 附加回退机制 。这是为 int 定义的，如您所见：
>>> (2).__cmp__
<method-wrapper '__cmp__' of int object at 0x13ee140>
>>> (2).__cmp__(3)
-1
(Python 2.7.12)
此外python-2.x offers a cmp(..) builtin function:
cmp(x, y)
Compare the two objects x and y and return an integer according to
the outcome. The return value is negative if x < y, zero if x == y
and strictly positive if x > y.
（已添加格式）
在python-3.x, the __cmp__ has been removed as you can read in the What’s New In Python 3.0中：
The cmp() function should be treated as gone, and the __cmp__()
special method is no longer supported. Use __lt__() for sorting,
__eq__() with __hash__(), and other rich comparisons as needed. (If you really need the cmp() functionality, you could use the expression
(a > b) - (a < b) as the equivalent for cmp(a, b).)
（已添加格式）
此机制不仅仅是 __cmp__ 的包装器：它会首先查看是否存在 丰富的比较 ，如果没有则回退到 __cmp__ 本身。
在 python 2 或 3 中内置 类 有明确定义的特殊方法。 Explicit is better than implicit 和所有爵士乐。
5. > 4.
# True
(5.).__ge__(4.)
# True
但在 python2 中，某些方法存在例外情况，至少在整数方面是这样。
5 > 4
# True
(5).__ge__(4)
# AttributeError: 'int' object has no attribute '__ge__'
# But not all of them fail!
(5).__add__(4)
# 9
这种行为背后的原因是什么？为什么要这样设计？
我正在使用 Python 2.7.12
data model has been updated between python-2.x and python-3.x. In python-2.x one could use the __cmp__ method:
object.__cmp__(self, other)Called by comparison operations if rich comparison (see above) is not defined. Should return a negative integer if
self < other, zero ifself == other, a positive integer ifself > other. If no__cmp__(),__eq__()or__ne__()operation is defined, class instances are compared by object identity ("address"). See also the description of__hash__()for some important notes on creating hashable objects which support custom comparison operations and are usable as dictionary keys. (Note: the restriction that exceptions are not propagated by__cmp__()has been removed since Python 1.5.)
（已添加格式）
rich comparison 运算符是 __le__, __ge__, etc.. So in python-2.x 还有一个 附加回退机制 。这是为 int 定义的，如您所见：
>>> (2).__cmp__
<method-wrapper '__cmp__' of int object at 0x13ee140>
>>> (2).__cmp__(3)
-1
(Python 2.7.12)
此外python-2.x offers a cmp(..) builtin function:
cmp(x, y)Compare the two objects
xandyand return an integer according to the outcome. The return value is negative ifx < y, zero ifx == yand strictly positive ifx > y.
（已添加格式）
在python-3.x, the __cmp__ has been removed as you can read in the What’s New In Python 3.0中：
The
cmp()function should be treated as gone, and the__cmp__()special method is no longer supported. Use__lt__()for sorting,__eq__()with__hash__(), and other rich comparisons as needed. (If you really need thecmp()functionality, you could use the expression(a > b) - (a < b)as the equivalent forcmp(a, b).)
（已添加格式）
此机制不仅仅是 __cmp__ 的包装器：它会首先查看是否存在 丰富的比较 ，如果没有则回退到 __cmp__ 本身。