Python解释器错误 [英] Python interpreter bug

问题描述

你好，


我认为我认为这是python解释器中的一个严重错误。


成员资格测试似乎不起作用当这些

对象具有用户定义的__cmp__方法时的对象列表。

它存在于Python 2.3和2.4中。我不知道其他版本。

以下代码说明了这个错误：
来自随机导入选择的


类OBJ：

def __init __（self，identifier）：

self.id = identifier

self.allocated = 0

def __cmp__ （自我，其他）：

返回cmp（other.allocated，self.allocated）

mylist = [OBJ（i）for i in range（20）]

excluded = [obj for mjist中的obj如果obj.id> choice（范围（20））]

for mjist中的obj：

if obj排除在外：

断言obj.id在[objt.id中为objt排除]

继续


运行上面的代码片段将触发断言。罪魁祸首似乎

是__cmp__方法，它对一个具有恒定价值的键进行排序。

最好的问候

Alain

Hello,

I came accross what i think is a serious bug in the python interpreter.

Membership testing seems not to work for list of objects when these
objects have a user-defined __cmp__ method.
It is present in Python 2.3 and 2.4. I don''t know about other versions.
The following code illustrates the bug:
from random import choice
class OBJ:
def __init__(self,identifier):
self.id=identifier
self.allocated=0
def __cmp__(self,other):
return cmp(other.allocated,self.allocated)
mylist=[OBJ(i) for i in range(20)]
excluded=[obj for obj in mylist if obj.id>choice(range(20))]
for obj in mylist:
if obj in excluded:
assert obj.id in [objt.id for objt in excluded]
continue

Running the above snippet will trigger the assert. The culprit seems to
be the __cmp__ method which sorts on a key with constant value.
Best regards
Alain

推荐答案

为什么会出现错误？你已经做到了这一点，OBJ的每个实例都等于OBJ的每个其他实例。行为符合预期。

Why would it be a bug? You''ve made it so that every instance of OBJ is
equal to every other instance of OBJ. The behaviour is as expected.

al ** ******@yahoo.fr 写道：

你好，

我认为这是我认为是python解释器中的一个严重错误。

当这些对象具有用户定义的__cmp__方法时，成员资格测试似乎不适用于对象列表。
它存在于Python 2.3和2.4中。我不知道其他版本。
下面的代码说明了这个bug：
来自随机导入选择
类OBJ：
def __init __（self，identifier）：
self.id = identifier
self.allocated = 0
def __cmp __（self，other）：
返回cmp（other.allocated，self.allocated）
mylist = [ OBJ（i）for i in range（20）]
excluded = [obj in mjist in obj.id> choice（range（20））]
for obj in mylist：
如果obj被排除在外：
断言obj.id in [objt.id for objt in excluded]
继续

我假设你只是把继续在那里玩得开心？

Hello,

I came accross what i think is a serious bug in the python interpreter.

Membership testing seems not to work for list of objects when these
objects have a user-defined __cmp__ method.
It is present in Python 2.3 and 2.4. I don''t know about other versions.
The following code illustrates the bug:
from random import choice
class OBJ:
def __init__(self,identifier):
self.id=identifier
self.allocated=0
def __cmp__(self,other):
return cmp(other.allocated,self.allocated)
mylist=[OBJ(i) for i in range(20)]
excluded=[obj for obj in mylist if obj.id>choice(range(20))]
for obj in mylist:
if obj in excluded:
assert obj.id in [objt.id for objt in excluded]
continue
I presume you just put the "continue" in there for fun?

对于mylist中的obj：
.... print obj in excluded

....

True

True

True

True

真实

真实

真实

真实

真实

真实

真实

真实

真实

真实

真实
True

True

True

True

True OBJ（0）== OBJ（ 1）

for obj in mylist: .... print obj in excluded
....
True
True
True
True
True
True
True
True
True
True
True
True
True
True
True
True
True
True
True
True OBJ(0) == OBJ(1)

True

运行上面的代码片段将触发断言。罪魁祸首似乎是__cmp__方法，它对具有恒定值的键进行排序。

True
Running the above snippet will trigger the assert. The culprit seems to
be the __cmp__ method which sorts on a key with constant value.

确实如此。据我所知，你的对象将全部测试相等。

你的意思是__cmp__方法返回cmp（other.id，self.id）？


问候

Steve

-

Steve Holden [phone] [phone]

Holden Web LLC www.holdenweb.com

PyCon TX 2006 www.python.org/pycon/

Well indeed. As far as I can see your objects will all test equal. Did
you mean the __cmp__ method to return cmp(other.id, self.id)?

regards
Steve
--
Steve Holden [phone] [phone]
Holden Web LLC www.holdenweb.com
PyCon TX 2006 www.python.org/pycon/

肯定有一个bug。

也许follownig片段更清晰：

类OBJ：

def __init __（自我，标识符）：

self.id = identifier

self.allocated = 0

#def __cmp __（self，other）：

＃return cmp（ other.allocated，self.allocated）

mylist = [OBJ（i）for i in range（10）]

excluded = [obj for obj in mylist if obj。 id [2,4,6,8]]

exclusion_list_by_id = [2,4,6,8]

print''排除列表by id =''，exclusion_list_by_id

for mjist中的obj：

print''current obj =''，obj.id，

if obj in excluded：

print''--->这个对象被排除''

断言obj.id in exclusion_list_by_id

继续

打印


如果取消注释这两行，断言将被错误地触发
。

Alain

There is definitely a bug.
Maybe the follownig snippet is more clear:
class OBJ:
def __init__(self,identifier):
self.id=identifier
self.allocated=0
#def __cmp__(self,other):
# return cmp(other.allocated,self.allocated)
mylist=[OBJ(i) for i in range(10)]
excluded=[obj for obj in mylist if obj.id in [2,4,6,8]]
exclusion_list_by_id=[2,4,6,8]
print ''exclusion list by id='',exclusion_list_by_id
for obj in mylist:
print ''current obj='',obj.id,
if obj in excluded:
print '' ---> THIS OBJECT IS EXCLUDED''
assert obj.id in exclusion_list_by_id
continue
print

If you uncomment the two lines, the assert will be erroneously
triggered.
Alain

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