import requests
from bs4 import BeautifulSoup
from base64 import b64decode

url = "https://yukicoder.me/problems/no/3107"
r = requests.get(url)

soup = BeautifulSoup(r.text, 'lxml')
imgs = soup.find_all('img')

dat = b''

for img in imgs:
    s = img.get('src')
    if s.startswith('data:audio/mpeg;base64'):
        dat = b64decode(s.replace('data:audio/mpeg;base64,', ''))

with open('apf.mpg', 'wb') as f:
    f.write(dat)
    
スクレイピング用コード