imgs = []
for a in tqdm(arts):
    so = BeautifulSoup(a['text'], 'html5lib')
    for t in so('img'):
        imgs.append(t['src'])

imgs = list(map(lambda i: re.sub(r'^/pictures/enc_mathematics/(\d+-\d+\.jpg)$', r'\1', i), imgs))
json.dump(imgs, open('imgs.json', 'w'), indent=4)

imgs = json.load(open('imgs.json', 'r'))

def dl_image(name):
    pic_url = 'https://dic.academic.ru/pictures/enc_mathematics/{}'.format(name)
    filename = './pics/{}'.format(name)
    with open(filename, 'wb') as handle:
        try:
            response = requests.get(pic_url, stream=True)
        except Exception:
            print (name)
            return name

        if not response.ok:
            print (name)
            return name

        for block in response.iter_content(1024):
            if not block:
                print (name)
                return name

            handle.write(block)

        return 'ok'

with Pool(8) as p:
    r = list(tqdm(p.imap(dl_image, imgs), total=len(imgs)))