result, number = re.subn(regex, newstring, subject) 

rereobj = re.compile(regex) 
result, number = reobj.subn(newstring, subject)

reresult = re.split(regex, subject) 

rereobj = re.compile(regex) 
result = reobj.split(subject) 

if re.search(regex, subject): 
do_something() 
else:
do_anotherthing()

if re.match(regex, subject): 
do_something() 
else: 
do_anotherthing() 

match = re.search(regex, subject) 
if match: 
# match start: match.start() 
# match end (exclusive): match.end() 
# matched text: match.group() 
do_something() 
else: 
do_anotherthing()