展平字符串列表的列表 [英] Flatten list of list of strings

问题描述

我有这个列表:

list1 = ["['word']", "['second', 'first']", "['first']"]

随着项目被转换为字符串，您会发现它并不完全是字符串列表.

You can see it's not exactly a list of list of strings as the items were converted into strings.

我想要这个拼合的输出:

I want to have this flattened output:

list2 = ['word', 'second', 'first', 'first']

只是一个简单的字符串列表.

Just a simple list of strings.

我尝试过使用这种方式:

I 've tried using this way:

list2 = [ x.strip('[]') for x in list1]

但是问题在于第二项仍被视为一项:

But the issue is with the second item still considered as one item:

["'word'", "'second', 'first'", "'first'"]

所以我尝试用逗号分割:

So I tried splitting by comma:

list3 = [item.split(',') for x in list2 for item in x]

但是它给出了以下输出:

But it gave this output:

[["'"],
 ['w'],
 ['o'],
 ['r'],
 ['d'],
 ["'"],
 ["'"],
 ['s'],
 ['e'],
 ['c'],
 ['o'],
 ['n'],
 ['d'],
 ["'"],
 ['', ''],
 [' '],
 ["'"],
 ['f'],
 ['i'],
 ['r'],
 ['s'],
 ['t'],
 ["'"],
 ["'"],
 ['f'],
 ['i'],
 ['r'],
 ['s'],
 ['t'],
 ["'"]]

有什么办法解决这个问题吗?

Any idea how to fix this?

在@AKX的帮助下

list2 = [ast.literal_eval(item) for item in list1]

然后使用此功能:

def flatten(lst):
    for el in lst:
        if isinstance(el, list):
            yield from el
        else:
            yield el

list3 = flatten(list2)
list(list3)

这给出了:

['word', 'second', 'first', 'first']

更新2

@waynelpu提供的一种优化的替代解决方案，而不是 flatten 函数，只需使用:

list2 = [inner for item in list1 for inner in ast.literal_eval(item)] 

推荐答案

如果您有一个表示列表的Python表达式字符串列表(嵌套子句的表达式如何)，则必须使用 ast.literal_eval()回到现实.

If you have a list of strings of Python expressions that represent lists (how's that for a nested clause), you will have to use ast.literal_eval() to get back to reality, as it were.

>>> import ast
>>> list1 = ["['word']", "['second', 'first']", "['first']"]
>>> list2 = [ast.literal_eval(item) for item in list1]
[['word'], ['second', 'first'], ['first']]

使用 ast.literal_eval()，而不是您不应该使用的危险 eval() 是安全的，因为它只计算没有副作用的文字.

Using ast.literal_eval(), as opposed to the dangerous eval() that you shouldn't use is safe, as it only evaluates literals that can have no side effects.

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