将数字1添加到集合中没有效果。

I cannot add the integer number 1 to an existing set. In an interactive shell, this is what I am doing:

我无法将整数数字1添加到现有的集合中。在交互shell中，我所做的是:

>>> st = {'a', True, 'Vanilla'}
>>> st
{'a', True, 'Vanilla'}
>>> st.add(1)
>>> st
{'a', True, 'Vanilla'}   # Here's the problem; there's no 1, but anything else works
>>> st.add(2)
>>> st
{'a', True, 'Vanilla', 2}

This question was posted two months ago, but I believe it was misunderstood. I am using Python 3.2.3.

这个问题是两个月前提出来的，但我认为是误解了。我正在使用Python 3.2.3。

4 个解决方案

#1

>>> 1 == True
True

I believe your problem is that 1 and True are the same value, so 1 is "already in the set".

我认为你的问题是1和真是相同的值，所以1是“已经在集合中”。

>>> st
{'a', True, 'Vanilla'}
>>> 1 in st
True

In mathematical operations True is itself treated as 1:

在数学运算中，真本身被视为1:

>>> 5 + True
6
>>> True * 2
2
>>> 3. / (True + True)
1.5

Though True is a bool and 1 is an int:

虽然正确是bool, 1是int:

>>> type(True)
<class 'bool'>
>>> type(1)
<class 'int'>

Because 1 in st returns True, I think you shouldn't have any problems with it. It is a very strange result though. If you're interested in further reading, @Lattyware points to PEP 285 which explains this issue in depth.

因为st中的1返回True，我认为你不应该有任何问题。这是一个非常奇怪的结果。如果您有兴趣进一步阅读，@Lattyware指向PEP 285，它深入地解释了这个问题。

#2

I believe, though I'm not certain, that because hash(1) == hash(True) and also 1 == True that they are considered the same elements by the set. I don't believe that should be the case, as 1 is True is False, but I believe it explains why you can't add it.

我认为，虽然我不确定，因为hash(1) = hash(True)和1 == True，它们在集合中被认为是相同的元素。

#3

1 is equivalent to True as 1 == True returns true. As a result the insertion of 1 is rejected as a set cannot have duplicates.

1等于True, 1 = True返回True。因此，插入1被拒绝，因为集合不能有重复。

#4

Here are some link if anyone is interested in further study.

如果有人对进一步的研究感兴趣，这里有一些联系。

Is it Pythonic to use bools as ints?

用bools当ints是python语言吗?

https://*.com/a/2764099/1355722

#1

>>> 1 == True
True