Created
December 11, 2015 16:47
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api.data.gov Elasticsearch JSON -> CSV multithreaded converter
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| import csv, json, sys, codecs, cStringIO, multiprocessing | |
| class UnicodeWriter: | |
| def __init__(self, f, dialect=csv.excel, encoding="utf-8-sig", **kwds): | |
| self.queue = cStringIO.StringIO() | |
| self.writer = csv.writer(self.queue, dialect=dialect, **kwds) | |
| self.stream = f | |
| self.encoder = codecs.getincrementalencoder(encoding)() | |
| def writerow(self, row): | |
| '''writerow(unicode) -> None | |
| This function takes a Unicode string and encodes it to the output. | |
| ''' | |
| self.writer.writerow([unicode(s).encode("utf-8") for s in row]) | |
| data = self.queue.getvalue() | |
| data = data.decode("utf-8") | |
| data = self.encoder.encode(data) | |
| self.stream.write(data) | |
| self.queue.truncate(0) | |
| def writerows(self, rows): | |
| for row in rows: | |
| self.writerow(row) | |
| pool = multiprocessing.Pool(4) | |
| output = UnicodeWriter(sys.stdout) | |
| def process_line(line): | |
| output.writerow(get_record(line).values()) | |
| def get_record(line): | |
| return json.loads(line)['_source'] | |
| with open(sys.argv[1]) as fh: | |
| # write the header line, then back up the file to the beginning | |
| data = get_record(fh.readline()) | |
| output.writerow(data.keys()) | |
| # now multiprocess all lines | |
| pool.map(process_line, fh) |
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