同时分配 [英] simultaneous assignment
问题描述
有没有办法将多个变量分配给相同的值，但是那么
身份测试仍然评估为False？
例如：< br>
w = x = y = z = False
w
False x
假w == x
真w是x
真＃不确定这是否有害
上面的第一行是我知道的唯一方法，但似乎
必然导致真正的身份测试。
John Salerno写道：
有没有办法将多个变量分配给相同的值，但是身份测试仍然可以评估为假？
例如：
>>> w = x = y = z = False
>>> w False>>> x False>>> w == x True>>> w是x真＃不确定这是否有害
上面的第一行是我知道的唯一方法，但它似乎必然会导致真正的身份测试。
是的，没有办法解决这个问题 - 假设python没有一个
可重载赋值运算符，例如C ++提供（赞美BDFL！）。在python中看起来像赋值的
语义是我在某个地方有一个花哨的
对象，现在我希望能够通过它来引用它那很好
这里的名字。实际上，对于
列表/字典元素分配，情况稍微复杂一些，但对于你的情况则无关紧要。
此外，取决于你分配的内容（例如整数，以及我猜的布尔值
身份测试结果如何。考虑一下：
a = 1000000
b = 1000000
a是b
假a = 100
b = 100 a是b
假a = 10
b = 10
a是b
True
我无法想象你在这之后的实际情况，但假设你确实需要这个并且我们正在谈论真实的话。这里的对象，序列
拆包和分配可能会派上用场，还有一个小的
list-comp：
a，b ，c = [copy.copy（o）for i in xrange（3）]
Diez
John Salerno写道：有没有办法将多个变量分配给相同的值，但是身份测试仍然评估为False？
例如：
>>> w = x = y = z = False
>>> w False>>> x False>>> w == x True>>> w是x真＃不确定这是否有害
上面的第一行是我知道的唯一方法，但它似乎必然会导致真正的身份测试。
class Foo：
def __eq __（* blah）：返回False
w = x = y = z = Foo（）
w == x
假w是x
True
Boris Borcic写道：
>>> w == x False>>> w是x True>>>
这与我想要发生的情况相反。
Is there a way to assign multiple variables to the same value, but so
that an identity test still evaluates to False?
e.g.:
w = x = y = z = False
w False x False w == x True w is x
True # not sure if this is harmful
The first line above is the only way I know to do it, but it seems to
necessarily lead to the true identity test.
John Salerno wrote:
Is there a way to assign multiple variables to the same value, but so
that an identity test still evaluates to False?
e.g.:>>> w = x = y = z = False
>>> w False >>> x False >>> w == x True >>> w is x True # not sure if this is harmful
The first line above is the only way I know to do it, but it seems to
necessarily lead to the true identity test.
Yes, and there is no way around that - given that python has not an
overloadable assignment operator as e.g. C++ offers (praise the BDFL!). The
semantics of what looks like assignment in python is "I''ve got a fancy
object somewhere, and now I want to be able to refer to it by that nice
name here". Actually things are somewhat more complicated in case of
list/dictionary element assignment, but for your case that is irrelevant.
Besides, depending on what you assign (e.g. integers, as well as the boolean
constants I guess) you might not even have the choice to guarantee how the
identity test results anyway. Consider this:
a = 1000000
b = 1000000
a is b False a = 100
b = 100
a is b False a = 10
b = 10
a is b True
I can''t imagine what you''re actually after here, but assuming that you
really need this and that we''re talking "real" objects here, sequence
unpacking and assignment might come handy here, together with a small
list-comp:
a, b, c = [copy.copy(o) for i in xrange(3)]
Diez
John Salerno wrote:Is there a way to assign multiple variables to the same value, but so
that an identity test still evaluates to False?
e.g.:>>> w = x = y = z = False
>>> w False >>> x False >>> w == x True >>> w is x True # not sure if this is harmful
The first line above is the only way I know to do it, but it seems to
necessarily lead to the true identity test.
class Foo : def __eq__(*blah) : return False
w = x = y = z = Foo()
w == x False w is x True
Boris Borcic wrote:
>>> w == x False >>> w is x True >>>
That''s the opposite of what I want to happen.
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