[PeterT]

Python uses indentation to "nest" code. Be consistent and use spaces rather than tabs.

Not being an expert I think the idea is you want something close to this:

from calibre.web.feeds.news import BasicNewsRecipe
from calibre.ebooks.BeautifulSoup import Tag, NavigableString

class WSWS(BasicNewsRecipe):

    title      = 'World Socialist Web Site'
    __author__ = 'International Committee of The Fourth International'
    description = 'WSWS'

    no_stylesheets = True
    remove_javascript     = True

    def parse_index(self):
        articles = []
        soup = self.index_to_soup('http://wsws.org/mobile/')
        cover = None
        feeds = []
        for section in soup.findAll('li'):
            section_title = self.tag_to_string(section.find('b'))
            articles = []
            for post in section.findAll('a', href=True):
                url = post['href']
                if url.startswith('/'):
                  url = 'http://www.wsws.org'+url
                  title = self.tag_to_string(post)
                  if str(post).find('class=') > 0:
                    klass = post['class']
                    if klass != "":
                      self.log()
                      self.log('--> post:  ', post)
                      self.log('--> url:   ', url)
                      self.log('--> title: ', title)
                      self.log('--> class: ', klass)
                      articles.append({'title':title, 'url':url})
            if articles:
                feeds.append((section_title, articles))
        return feeds

so the idea is you loop through all sections that are identified by "li" entries and then for each entry found use the loop

            for post in section.findAll('a', href=True):
                url = post['href']
                if url.startswith('/'):
                  url = 'http://www.wsws.org'+url
                  title = self.tag_to_string(post)
                  if str(post).find('class=') > 0:
                    klass = post['class']
                    if klass != "":
                      self.log()
                      self.log('--> post:  ', post)
                      self.log('--> url:   ', url)
                      self.log('--> title: ', title)
                      self.log('--> class: ', klass)
                      articles.append({'title':title, 'url':url})

to append each article to the list of articles