是不是bool __invert__行为“奇怪”？ [英] Isn't bool __invert__ behaviour "strange"?

问题描述

为什么要从int中继承bool __invert__或__neg__还没有被b / b
覆盖以产生布尔否定？我怀疑向后

兼容性或类似的东西，但我仍然想知道..


因为bool不能被子类化，所以有类似bool的类型但是用

布尔否定你有什么建议？包装器可能是？

（我会使用它，所以我可以评估用户定义的布尔表达式

在我的命名空间中创建他/她的变量的istances而不是eval（）

他/她的表达）

解决方案

Saizan写道：

为什么要从int中继承bool __invert__或__neg__没有？
被覆盖以产生布尔否定？

我想知道-True或-False应该评估什么。


问候，

Bj？rn


-

BOFH借口＃297：


太多中断

Bjoern Schliessmann写道：

Saizan写道：
< blockquote class =post_quotes>
为什么要从int中继承bool __invert__或__neg__没有

被覆盖以产生布尔否定？

我不知道-True或-False应该评估什么。


问候，


Bj？


-

BOFH借口＃297：


太多中断

布尔符号--True == False和-False == True，实际上你可能更喜欢？b $ b？或者术语上的一行，但由于python中没有这样的

运算符，我认为我们应该使用 - 这也是Bool自己使用的运算符

用于否定的公式，即1-x。

现在我认为1-x应该作为否定在Python中，

，因为True == 1和False == 0，但以这种方式写表达式会有点烦人。

Saizan写道：

为什么要从int中继承bool __invert__或__neg__还没有

覆盖产生布尔否定？我怀疑向后

兼容性或类似的东西，但我仍然想知道..


因为bool不能被子类化，所以有类似bool的类型但是用

布尔否定你有什么建议？一个包装器可能？


（我会使用它，所以我可以评估用户定义的布尔表达式

在我的命名空间中创建他/她的变量的istances而不是eval（）

他/她的表达式）

not运算符和bool（）内置产生

布尔结果。由于bool是int的子类，

所有整数运算都将保持整数

运算。这是为了后退

兼容性，并且不太可能在2.x

系列中改变。


我不喜欢不记得这是否应该在3.0中改变

。参见PEP 3100和3099.


John Roth


John Roth

Why subclassing bool from int either __invert__ or __neg__ haven''t been
overrided to produce a boolean negation? I suspect backwards
compatibility or something alike, but I still wonder..

And since bool can''t be subclassed, to have a type like bool but with
boolean negation what do you suggest? A wrapper maybe?
(I would use it so I can evaluate user-defined boolean expression
creating istances of his/her variables in my namespace and than eval()
his/her expression)

解决方案

Saizan wrote:

Why subclassing bool from int either __invert__ or __neg__ haven''t
been overrided to produce a boolean negation?

I wonder what -True or -False should evaluate to.

Regards,
Bj?rn

--
BOFH excuse #297:

Too many interrupts

Bjoern Schliessmann wrote:

Saizan wrote:

Why subclassing bool from int either __invert__ or __neg__ haven''t
been overrided to produce a boolean negation?

I wonder what -True or -False should evaluate to.

Regards,
Bj?rn

--
BOFH excuse #297:

Too many interrupts

Well in boolean notation -True == False and -False == True, actually
you may prefer ? or a line over the term, but since there''s no such
operator in python I think we should use "-" which is also the operator
used by Bool himself in his formulation for negation which was 1-x.
Now that I think of it 1-x should work as a negation in Python, too,
since True == 1 and False == 0, but it would be a little annoying to
write expressions in this way.

Saizan wrote:

Why subclassing bool from int either __invert__ or __neg__ haven''t been
overrided to produce a boolean negation? I suspect backwards
compatibility or something alike, but I still wonder..

And since bool can''t be subclassed, to have a type like bool but with
boolean negation what do you suggest? A wrapper maybe?
(I would use it so I can evaluate user-defined boolean expression
creating istances of his/her variables in my namespace and than eval()
his/her expression)

The not operator and the bool() builtin produce
boolean results. Since bool is a subclass of int,
all the integer operations will remain integer
operations. This was done for backwards
compatability, and is unlikely to change in the 2.x
series.

I don''t remember if this is supposed to change
in 3.0. See PEP 3100 and 3099.

John Roth

John Roth

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