Build HTML Reverser

#recursion
def reverse(html):
    if not html:
        return

    tag, html = stripOuterTag(html)
    listOfTrunks = divideTrunks(html)
    #print listOfTrunks
    if len(listOfTrunks) == 1:
        return listOfTrunks[0][::-1] if not tag else addTag(listOfTrunks[0][::-1], tag)
    
    listOfTrunks = listOfTrunks[::-1]
    listOfTrunks = [reverse(trunk) for trunk in listOfTrunks]
    
    return addTag("".join(listOfTrunks), tag)

#split up elements in the same level
'''e.g. "hello
xyzab
hi"
into 
["hello", "
xyzab
", "hi"]
'''
def divideTrunks(html):
    ls = []
    while html:
        idxOfOpenP = html.find('<')
        if idxOfOpenP > 0:
            ls.append(html[0: idxOfOpenP])
            html = html[idxOfOpenP:]
        else:
            tag = html[1: html.find('>')]
            endTag = ''
            idxOfEndTag = html.find(endTag)
            ls.append(html[0: idxOfEndTag   len(endTag)])
            html = html[idxOfEndTag   len(endTag):]
    return ls

'''
remove and return the surrounding tag
e.g.   "\hi\" 
into 
\, "hi"
'''
def stripOuterTag(html):
    if not html or html[0] != '<':
        return None, html
    tag = html[: html.find('>')   1]
    return tag, html[len(tag): len(html) - len(tag) -1]