python中for循环中的[]括号是什么意思? [英] What do [] brackets in a for loop in python mean?
问题描述
我正在解析 JSON 对象并找到了这行代码示例,我有点理解但希望得到更详细的解释:
I'm parsing JSON objects and found this sample line of code which I kind of understand but would appreciate a more detailed explanation of:
for record in [x for x in records.split("\n") if x.strip() != '']:
我知道它正在拆分记录以通过换行符获取单个记录,但是我想知道为什么它看起来如此复杂?是不是我们不能有这样的事情:
I know it is spliting records to get individual records by the new line character however I was wondering why it looks so complicated? is it a case that we can't have something like this:
for record in records.split("\n") if x.strip() != '']:
那么括号 [] 的作用是什么?以及为什么我们在 x for x in records.split .....
So what do the brackets do []? and why do we have x twice in x for x in records.split....
谢谢
推荐答案
示例中的括号"从旧列表构建新列表,称为 列表理解.
The "brackets" in your example constructs a new list from an old one, this is called list comprehension.
[f(x) for x in xs if condition]
的基本思想是:
def list_comprehension(xs):
result = []
for x in xs:
if condition:
result.append(f(x))
return result
f(x)
可以是任何表达式,包含或不包含 x
.
The f(x)
can be any expression, containing x
or not.
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