class Foo():
    _rex = re.compile("d+")
    def bar(self, string):
         m = _rex.match(string)
         if m != None:
             doStuff()

>>> s="1234n"
>>> re.search("^d+Z",s)
>>> s="1234"
>>> re.search("^d+Z",s)
<_sre.SRE_Match object at 0xb762ed40>

re.match(r'd+$') # re.match anchors the match at the start of the string, so $ is what remains to add

re.match(r'd+Z') # Z will only match at the very end of the string

re.search(r'^d+$')
re.search(r'Ad+Z')

_rex = re.compile("d+")
if _rex.fullmatch(s):
    doStuff()