import re
z="CONN <DO_NOT_PRINT>user</DO_NOT_PRINT>/<DO_NOT_PRINT>password</DO_NOT_PRINT>@//host:port/service"
REPLACEME = re.compile('<DO_NOT_PRINT>(.*?)</DO_NOT_PRINT>', re.DOTALL)
print( REPLACEME.sub(lambda x: '*' * len(x.group(1)), z) )
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