python - lxml/ python : get previous-sibling

Question

我有以下 html:

<div id = "big">
    <span>header 1</span>
    <ul id = "outer">
        <li id = "inner">aaa</li>
        <li id = "inner">bbb</li>
    </ul>

    <span>header 2</span>
    <ul id = "outer">
        <li id = "inner">ccc</li>
        <li id = "inner">ddd</li>
    </ul>
</div>

我希望它按顺序循环:

header 1
aaa
bbb
header 2
ccc
ddd

我尝试遍历每个 ul，然后打印标题和 li 值。但是，我不知道如何获取与 ul 关联的跨度 header 。

sets = tree.xpath("//div[@id='big']//ul[@id='outer']")

for set in sets:

    # Print header. Not sure how to get it
    header = set.xpath(".//li/preceding-sibling::span")
    print header 

    # Print texts. This works.
    values = set.xpath(".//li//text()")
    for v in values:
        print v 

仅仅循环所有文本节点是行不通的，因为我需要知道它是标题还是 li 值。

Answer 1

这有效:

header = ingred_set.getprevious().xpath(".//text()")[0]