Exact match with regular expression

[Mr.SpOOn]

Hi,
I'd like to use regular expressions to parse a string and accept only
valid strings. What I mean is the possibility to check if the whole
string matches the regex.

So if I have:

>>> p = re.compile('a*b*')

I can match this: 'aaaaaabbb'

>>> m = p.match('aaaaaabbb')
>>> m.group()
'aaaaaabbb'

But I'd like to get None with this: 'aabDDDDb'
Instead it matches the first part:

>>> m = p.match('aabDDDDb')
>>> m.group()
'aab'

I know this is the expected behaviour, but I'm sure it should be
possible doing what I said.
Are there other methods I don't know about in the re module?

Thanks.