#!/usr/bin/python3

import lxml.etree as lxml
import sys
import random

input_file_name = sys.argv[1]
sample_size = int(sys.argv[2])
output_file_name = sys.argv[3]

tree = lxml.parse(input_file_name)
root = tree.getroot()
indexes = list(range(len(root.xpath('entry'))))
random.shuffle(indexes)

for (index, entry) in enumerate(root.xpath('entry')):
    if (index not in indexes[:sample_size]):
        root.remove(entry)

tree.write(output_file_name, encoding='UTF-8')