Xpath无法定位含a标签的span中的任意元素

成功定位到span标签

download = new_html.xpath('//*[@id="Zoom"]/span')
print(download)
output:[<Element span at 0x7fa9370bae80>]

但是如果这个span中包裹了a标签,就什么都无法匹配了

download = new_html.xpath('//*[@id="Zoom"]/span/a/@href')
print(download)
output: []

源码是这样的

<span>
    <img src="xxx" alt="xxx">
    For test.
    <br />
    For test.
    <br />
    <a target="_blank" href="abcabc">click on me.</a>   
</span>

请问我如果想用xpath拿到这个span中的a的href值该怎么办呢

from lxml import etree

con = """<html>
<body><span>
    <img src="xxx" alt="xxx">
    For test.
    <br />
    For test.
    <br />
    <a target="_blank" href="abcabc">click on me.</a>   
</span>
</body>
</html>"""

tree = etree.HTML(con)
download = tree.xpath('//span/a/@href')
print(download)

'''--result
['abcabc']
'''