from lxml import etree 
text = '''
<div>
    <ul>
         <li class="item-0"><a href="link1.html">first item</a></li>
         <li class="item-1"><a href="link2.html">second item</a></li>
         <li class="item-inactive"><a href="link3.html">third item</a></li>
         <li class="item-1"><a href="link4.html">fourth item</a></li>
         <li class="item-0"><a href="link5.html">fifth item</a> <!--注意 这里少了一个<li>标签-->
     </ul>
 </div>
'''
html = etree.HTML(text) 

#bytes_res = etree.tostring(html) 
#print(bytes_res)
str_res = etree.tostring(html,encoding='utf-8').decode('utf-8')
print(str_res)
f = open("demo.txt", "w",encoding="utf-8")
f.write(str_res)

f.close()