from bs4 import BeautifulSoup
html='''
    <h1> A </h1>
    <p >AA </p>
    <li>a1</li>
    <li>a2</li>


    <h2> B </h2>
    <p >BB </p>
    <li > b1</li>
    <li > b2</li>
    <li > b3</li>

    <h3> C </h3>
    <p >CC</p>
    <li>   c1</li>
'''
soup=BeautifulSoup(html,'lxml',from_encoding='utf-8')

for p in soup.findAll('p'):
        print(p.text,end="")
        for dt in p.find_all_next("li"):
            print("\t",dt.text,end=",")
        print()

 期望输出  AA a1,a2
          BB b1,b2,b3
          CC c1
          

但是结果输出是
AA a1, a2, b1, b2, b3, c1,
BB b1, b2, b3, c1,
CC c1,