用if和break创建Python列表理解 [英] Creating a Python list comprehension with an if and break
问题描述
for user input:
if i in wordsTask:
a = i
break
我知道如何将部分它:
[我为我在userInput中,如果我在wordsTask]
但是我不知道如何添加break,文档也没有太大的帮助。
a = next(i for i在用户输入,如果我在wordsTask)
有点分解:
[我为我在userInput,如果我在wordsTask]
会产生一个列表。你想要的是列表中的第一项。一种方法是使用下一个函数:
pre $ next([i for userInput if i in wordsTask])
接下来从一个迭代器返回下一个项目。在像列表一样迭代的情况下,它最终取得了第一个项目。
但是没有理由建立这个列表,所以我们可以使用一个生成器表达式而不是:
a = next(我为我在userInput如果我在wordsTask)
另外,请注意,如果生成器表达式为空,则会导致一个异常: StopIteration
。你可能想要处理这种情况。或者你可以添加一个默认的
a = next((我为我在userInput,如果我在wordsTask中),42)
Is it possible to turn this code into a list comprehension?
for i in userInput:
if i in wordsTask:
a = i
break
I know how to convert part of it:
[i for i in userInput if i in wordsTask]
But I don't know how to add the break, and the documentation hasn't been much help.
Any help would be appreciated.
a = next(i for i in userInput if i in wordsTask)
To break it down somewhat:
[i for i in userInput if i in wordsTask]
Will produce a list. What you want is the first item in the list. One way to do this is with the next function:
next([i for i in userInput if i in wordsTask])
Next returns the next item from an iterator. In the case of iterable like a list, it ends up taking the first item.
But there is no reason to actually build the list, so we can use a generator expression instead:
a = next(i for i in userInput if i in wordsTask)
Also, note that if the generator expression is empty, this will result in an exception: StopIteration
. You may want to handle that situation. Or you can add a default
a = next((i for i in userInput if i in wordsTask), 42)
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