Regex for getting matches within a group

Question

I do not know if the following is possible. Suppose I have the following text:

<ul class="yes">
    <li><img src="whatever1"></li>
    <li><img src="whatever2"></li>
    <li><img src="whatever3"></li>
    <li><img src="whatever4"></li>
</ul>
<ul class="no">
    <li><img src="whatever5"></li>
    <li><img src="whatever6"></li>
    <li><img src="whatever7"></li>
    <li><img src="whatever8"></li>
</ul>

I would like to map each img src inside ul to the class yes. I want one regex to return me:

whatever1
whatever2
whatever3
whatever4

How can I append two regular expressions like these in one regular expression?

<ul class="yes">(.+?)<\/ul>
<img src="(whatever.+?)">

Answer 1

It is known that Regex is difficult to use for parsing XML-like materials. Better skip the idea and collapse using your own HTML parser, for example using BeautifulSoup4 :

import bs4

html = """
<ul class="yes">
    <li><img src="whatever1"></li>
    <li><img src="whatever2"></li>
    <li><img src="whatever3"></li>
    <li><img src="whatever4"></li>
</ul>
<ul class="no">
    <li><img src="whatever5"></li>
    <li><img src="whatever6"></li>
    <li><img src="whatever7"></li>
    <li><img src="whatever8"></li>
</ul>
"""

soup = bs4.BeautifulSoup(html)

def match_imgs(tag):
    return tag.name == 'img' \
        and tag.parent.parent.name == 'ul' \
        and tag.parent.parent['class'] == ['yes']

imgs = soup.find_all(match_imgs)
print(imgs)

whatevers = [i['src'] for i in imgs]
print(whatevers)

Productivity:

[<img src="whatever1"/>, <img src="whatever2"/>, <img src="whatever3"/>,
<img src="whatever4"/>]

[u'whatever1', u'whatever2', u'whatever3', u'whatever4']