StandardEbooks scraper

from bs4 import BeautifulSoup
import requests as req

import os

BASE_URL = "https://standardebooks.org"

for i in range(1, 43):
    r = req.get(BASE_URL + "/ebooks?page=" + str(i))

    soup = BeautifulSoup(r.text, "html.parser")

    urls = [link.get('href') for link in soup.find_all('a')]

    book_urls = [url for url in urls[:-49] if type(url) is str and "ebooks" in url and url.count('/') >= 2]

    unique_book_urls = book_urls[::3]

    for working_url in unique_book_urls:
        rr = req.get(BASE_URL + working_url)

        new_soup = BeautifulSoup(rr.text, "html.parser")

        page_urls = [link.get('href') for link in new_soup.find_all('a')]

        try:
            epub_link = [url for url in page_urls if ".epub" in url][0]
        except Exception:
            break

        wget_string = "wget --no-clobber {}".format(BASE_URL + epub_link)

        os.system(wget_string)