“a是b”的结果 [英] Result of ``a is b''
问题描述
你好，
有以下行为的理由：
a =（1,2）
b =（1,2）
a是b
假a =12
b =" 12"
a是b
True
谢谢，
Axel
" Axel Boldt" <斧******* @ yahoo.com>在消息中写道
news：40 ************************** @ posting.google.c om ...
是否存在以下行为的基本原理：
>>> a =（1,2）
>>> b =（1,2）
>>> a是b False>>> a =12
>>> b =" 12"
>>> a是b True
可能是实施意外。考虑：
a =" 1 2"
b =" 1" + 2
a是b
False
，就此而言：
a =（1,2）
b = a
a是b
正确
你有什么理由关心关于这种行为？
Axel Boldt写道：
是否存在以下行为的理由：
是的：对你来说实施工作并不重要。
-
__ Erik Max Francis&& ma*@alcyone.com && http://www.alcyone.com/max/
/ \美国加利福尼亚州圣何塞市&& 37 20 N 121 53 W&& & tSftDotIotE
\ __ /我唯一遗憾的是，我的国家只有一次失败。
- Nathan Hale
> >>> a =（1,2）>>> b =（1,2）
>>> a是b False>>> a =12
>>> b =" 12"
>>> a是b True
除非你关心两个名字是否指向同一个对象，否则不要使用
''是'' 。而是将'==''与等式进行比较。这应该像
你想要的那样：a =（1,2）
b =（1,2）
a == b
True a =" 12"
b =" 12"
a == b
真的
它还将处理Andrew指出的案例。
- Josiah
Hello,
is there a rationale for the following behavior:
a = (1,2)
b = (1,2)
a is b False a = "12"
b = "12"
a is b
True
Thanks,
Axel
"Axel Boldt" <ax*******@yahoo.com> wrote in message
news:40**************************@posting.google.c om...
is there a rationale for the following behavior:>>> a = (1,2)
>>> b = (1,2)
>>> a is b False >>> a = "12"
>>> b = "12"
>>> a is b True
Probably an accident of implementation. Consider:
a = "1 2"
b = "1" + " 2"
a is b False
and, for that matter:
a = (1, 2)
b = a
a is b
True
Is there a reason that you care about this behavior?
Axel Boldt wrote:
is there a rationale for the following behavior:
Yes: It shouldn''t matter to you what the implementation is doing.
--
__ Erik Max Francis && ma*@alcyone.com && http://www.alcyone.com/max/
/ \ San Jose, CA, USA && 37 20 N 121 53 W && &tSftDotIotE
\__/ I only regret that I have but one life to lose for my country.
-- Nathan Hale
> >>> a = (1,2)>>> b = (1,2)
>>> a is b False >>> a = "12"
>>> b = "12"
>>> a is b True
Unless you care whether two names point to the same object, don''t use
''is''. Instead compare for equality with ''==''. That should work like
you want it to:a = (1,2)
b = (1,2)
a == b True a = "12"
b = "12"
a == b
True
It will also handle the cases that Andrew points out.
- Josiah
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