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@mgax /large_xml.py
Last active Mar 4, 2016

Writing a large XML file using SAX
import argparse
import tempfile
import shutil
import subprocess
import lxml.etree
from lxml.builder import ElementMaker
from xml.sax import parse
from xml.sax.saxutils import XMLGenerator
from xml.sax.handler import ContentHandler
def generate_large_xml(f, size_mb):
E = ElementMaker()
doc = E.One(E.Two(E.Three(E.Four())))
doc_str = lxml.etree.tostring(doc, pretty_print=True).decode('ascii')
start, end = doc_str.split('<Four/>')
payload = E.Payload('big data here!!\n' * 62 + 'done ... ..\n')
payload_str = lxml.etree.tostring(payload).decode('ascii') + '\n'
f.write(start.encode('ascii'))
for c in range(1024 * size_mb):
f.write(payload_str.encode('ascii'))
f.write(end.encode('ascii'))
def main():
parser = argparse.ArgumentParser()
parser.add_argument('size_mb', type=int)
parser.add_argument('--no-write', action='store_true')
args = parser.parse_args()
tmp = tempfile.mkdtemp()
try:
with open(tmp + '/large.xml', 'wb') as f:
generate_large_xml(f, args.size_mb)
with open(tmp + '/large.xml', 'rb') as in_file:
with open(tmp + '/out.xml', 'wb') as out_file:
if args.no_write:
handler = ContentHandler()
else:
handler = XMLGenerator(out_file, encoding='utf-8')
parse(in_file, handler)
subprocess.check_call(['ls', '-l', tmp])
finally:
shutil.rmtree(tmp)
if __name__ == '__main__':
main()
$ time python large_xml.py 10
total 20488
-rw-r--r-- 1 alexm staff 10485822 Oct 21 21:41 large.xml
-rw-r--r-- 1 alexm staff 10485860 Oct 21 21:42 out.xml
python large_xml.py 10 7.19s user 0.07s system 99% cpu 7.277 total
$ time python large_xml.py 10 --no-write
total 10244
-rw-r--r-- 1 alexm staff 10485822 Oct 21 21:42 large.xml
-rw-r--r-- 1 alexm staff 0 Oct 21 21:42 out.xml
python large_xml.py 10 --no-write 0.61s user 0.04s system 98% cpu 0.660 total
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