>>> import re

マッチング

>>> if re.compile("cde").search("abcdef"):
...   print "Match"
...
Match
>>> if re.compile("cde").match("abcdef"):
...   print "Match"
...
>>> if re.compile("abc").match("abcdef"):
...   print "Match"
...
Match
>>>
>>> if re.compile("cde").search("ABCDEF"): print "Match"
...
>>> if re.compile("cde", re.I).search("ABCDEF"): print "Match"
...
Match
>>> 

何がマッチしたのか？

>>> 
>>> src = '----123a456----7b8--901c23--'
>>> mo = re.compile('\d+[a-z]\d+').search(src)
>>> mo.group()
'123a456'
>>> 
>>> mo = re.compile('(\d+)[a-z](\d+)').search(src)
>>> mo.group()
'123a456'
>>> mo.group(1)
'123'
>>> mo.group(2)
'456'
>>> 
>>> mo = re.compile('(\d+)[a-z](\d+)').findall(src)
>>> mo
[('123', '456'), ('7', '8'), ('901', '23')]
>>> 

置換

>>> print re.sub("[ace]", "*", "a-b-c-d-e-f")
*-b-*-d-*-f
>>>
>>> print re.sub("[ace]", "*", "a-b-c-d-e-f", 2)
*-b-*-d-e-f
>>>
>>> print re.compile("[ace]", re.I).sub("*", "A-B-C-D-E-F")
*-B-*-D-*-F