NULL on error flipping bits whilst updating pixels

Auto generating SEO-friendly URLs with Scrapy pipelines

I was using Scrapy to crawl some websites and mirror their content into a new one and at the same time, generate beautiful and unique URLs based on the title, but the title can appear repeated! So I added part of the original URL in base36 as uniqueness guarantees.

In the URL I wanted the title without special symbols, only ASCII and at the end a unique and short inditifier, and part of the result of the SHA-256 of the URL in base36.

class PreparePipeline():
  def process_item(self, item, spider):
    title = item.get("title")
    if title is None:
      raise DropItem(f"No title were found on item: {item}.")

    url = item["url"]

    N = 4
    sha256 = hashlib.sha256(url.encode()).digest()
    sliced = int.from_bytes(
        memoryview(sha256)[:N].tobytes(), byteorder=sys.byteorder)
    uid = base36.dumps(sliced)

    strip = str.strip
    lower = str.lower
    split = str.split
    deunicode = lambda n: normalize("NFD", n).encode("ascii", "ignore").decode("utf-8")
    trashout = lambda n: re.sub(r"[.,-@/\\|*]", " ", n)
    functions = [strip, deunicode, trashout, lower, split]
    fragments = [
        lambda x, f: f(x), functions, title),

    item["uid"] = "-".join(fragments)

    return item

For example, with the URLéjà_vu and title Déjà vu - Wikipedia will result in: deja-vu-wikipedia-1q9i86k. Which is perfect for my use case.