用正则表达式捕获嵌套标签？

Question

s = '''<p>Plain text, <i>italicized phrase,
 <i>italicized subphrase</i>, <b>bold
 subphrase</b></i>, <i>other italic
 phrase</i></p>'''

r1 = r'''(?sx)(
<i>(
(?!</?i>).
|
<i> ( (?!</?i>). )* </i>
)*</i>
)'''

I use r1 pattern to capture <i>...</i> in string s. But <i>italicized subphrase</i> can't be captured. Why?

I'm not dealing with HTML code really, but something similar with HTML's nest structure! I'm just taking these codes for example. My problem is how to capture both nested and nesting tags in only one layer nest structure.

Answer 1

You are using a regular expression, and matching XML with such expressions get too complicated, too fast .

Please don't make it hard on yourself and use a HTML parser instead, Python has several to choose from:

• ElementTree is part of the standard library
• BeautifulSoup is a popular 3rd party library
• lxml is a fast and feature-rich C-based library.

ElementTree example:

from xml.etree import ElementTree

tree = ElementTree.parse('filename.html')
for elem in tree.findall('i'):
    print ElementTree.tostring(elem)