Monkeypatch Stem's DirectoryReader to just care about the relays we're interested in.

MyDescriptorReader

import os
import tarfile

import stem
from stem.descriptor.reader import DescriptorReader

class MyDescriptorReader(DescriptorReader):
    def __init__(self, interesting_fingerprints, *args, **kwargs):
        DescriptorReader.__init__(self, *args, **kwargs)
        self._interesting_fingerprints = interesting_fingerprints
        
    def _handle_archive(self, target):
        # TODO: This would be nicer via the 'with' keyword, but tarfile's __exit__
        # method was added sometime after python 2.5. We should change this when
        # we drop python 2.5 support.

        tar_file = None

        try:
            self._notify_read_listeners(target)
            tar_file = tarfile.open(target)

            for tar_entry in [tar_entry for tar_entry in tar_file if tar_entry.name.split("/")[-1] in self._interesting_fingerprints]:
                if tar_entry.isfile():
                    entry = tar_file.extractfile(tar_entry)

                    try:
                        for desc in stem.descriptor.parse_file(entry, validate = self._validate, document_handler = self._document_handler, **self._kwargs):
                            if self._is_stopped.is_set():
                                return

                            desc._set_path(os.path.abspath(target))
                            desc._set_archive_path(entry.name)
                            self._unreturned_descriptors.put(desc)
                            self._iter_notice.set()
                    except TypeError as exc:
                        self._notify_skip_listeners(target, ParsingFailure(exc))
                    except ValueError as exc:
                        self._notify_skip_listeners(target, ParsingFailure(exc))
                    finally:
                        entry.close()
        except IOError as exc:
            self._notify_skip_listeners(target, ReadFailed(exc))
        finally:
            if tar_file:
                tar_file.close()

        

my_descriptors = [
    'extra-infos-2014-02.tar.bz2'
]

my_fingerprints = [
    '446691dfdbafbb4e5f021b5a2b73b5c8fc297b91'
]

# prints the contents of all the descriptor files
with MyDescriptorReader(my_fingerprints, my_descriptors) as reader:
    for descriptor in reader:
        print "Relay %s wrote %i and read %i bytes." % (descriptor.fingerprint, sum(descriptor.read_history_values), sum(descriptor.write_history_values))