#FILE: temp.py:

import re
from bs4 import BeautifulSoup

def reBIReplace(txt):
    txt = re.sub(r"</?b>","'''",txt)
    txt = re.sub(r"</?i>","''",txt)
    return txt

def soupBIReplace(txt):
    soup = BeautifulSoup(txt)
    btag = soup.b
    itag = soup.i
    txt = txt.replace(str(btag), "'''"+str(btag.string)+"'''")
    txt = txt.replace(str(itag), "''"+str(itag.string)+"''")
    return txt

#SHELL:

>>> import timeit
>>> timeit.Timer('temp.reBIReplace("foo <b>bar</b> <i>baz</i>")','import temp').timeit(100)
0.0029594631914433072
>>> timeit.Timer('temp.soupBIReplace("foo <b>bar</b> <i>baz</i>")','import temp').timeit(100)
0.08923220030303725
>>> print "regex is",0.08923220030303725 / 0.0029594631914433072,"times faster than soup."
regex is 30.151481715 times faster than soup.