[英]Set subtraction while casting lists and string
I have two lists of strings.我有两个字符串列表。 When I cast two lists into
set()
then subtraction works properly.当我将两个列表转换为
set()
时,减法可以正常工作。
>>> A = ['One', 'Two', 'Three', 'Four']
>>> B = ['One']
>>> print(list(set(A) - set(B)))
['Three', 'Two', 'Four']
However when variable B
is a string and I cast it into set()
then, the subtraction is not working.但是,当变量
B
是一个字符串并且我将其转换为set()
时,减法不起作用。
>>> A = ['One', 'Two', 'Three', 'Four']
>>> B = 'One'
>>> print(list(set(A) - set(B)))
['One', 'Two', 'Three', 'Four']
Is anyone able to explain me if its a bug or expected behavior?如果它是一个错误或预期的行为,有人能解释我吗?
This is expected.这是意料之中的。 It considers the string as an iterable and thus creates a set of all letters.
它将字符串视为可迭代的,因此创建了一组所有字母。
B = 'One'
set(B)
# {'O', 'e', 'n'}
You can clearly see it if you have letters in A
:如果您在
A
中有字母,您可以清楚地看到它:
A = ['One', 'Two', 'Three', 'Four', 'O', 'o', 'n']
B = 'One'
print(list(set(A) - set(B)))
Output: ['o', 'Two', 'One', 'Four', 'Three']
Output:
['o', 'Two', 'One', 'Four', 'Three']
The set()
function, when operating on a string, will generate a set of all characters: set()
function 在对字符串进行操作时,将生成一组所有字符:
print(set("ABC")) # set(['A', 'C', 'B'])
If you want a set with a single string ABC
in it, then you need to pass a collection containing that string to set()
:如果您想要一个包含单个字符串
ABC
的集合,那么您需要将包含该字符串的集合传递给set()
:
print(set(["ABC"])) # set(['ABC'])
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