Andrew Vaillancourt

Software Developer from Winnipeg, Manitoba, Canada andrewvcourt.com

Scraping a Website for High-Quality ROMs Using Python

Let’s say hypothetically you wanted to download all of the high quality Super Nintendo ROMs from a website. The site simply has a list of links that take you to the file itself. Since this is a flat tree, you could run a basic wget command with the URL ala:
wget -m -np -c -w 3 -R "index.html*" "https://rom-site.blah/path/to/roms/"
However, this would give you every game, regardless of quality. Fortunately, ROM enthusiasts use suffixes to denote the status of roms:
[a] Alternate
[p] Pirate
[b] Bad Dump     (avoid these, they may not work!)
[t] Trained
[f] Fixed
[T-] OldTranslation
[T+] NewerTranslation
[h] Hack
(-) Unknown Year
[o] Overdump
[!] Verified Good Dump
(M#) Multilanguage (# of Languages)
(###) Checksum
(??k) ROM Size
ZZZ_ Unclassified
(Unl) Unlicensed
So we just want the ones with the [!] suffix. You may also want to specify [U] for just the US releases as well.
There is certainly some way of specifying this to
wget
with a regular expression, but I am definitely no
wget
or regex pro, so after a few minutes of unsuccessful attempts, I gave up and wrote a short Python script to get me what I wanted using Beautiful Soup
Before writing any code I analyzed the source of the target URL, and
sure enough, the page was pretty much just a list of anchor tags, with a
direct link to the ROM file. Perfect.
After peeking at the
html
, I know I just need to extract the links from all the anchors, but only collect the ones containing the [!] suffix. This can be done in less than 15 lines of Python:
First, install beautifulsoup4:
 pip3 install beautfilsoup4
And then create a file called
good_roms.py
with the following code:
# good_roms.py
import requests
from bs4 import BeautifulSoup

weburl = 'https://site.site/path/to/roms/'
data = requests.get(weburl)
soup = BeautifulSoup(data.text, features='html.parser')

links = []
for anch in soup.find_all('a'):
    if '[!]' in str(anch):
        links.append(weburl + anch.get('href'))

for link in links:
    print(link)
Now I can just run the program and redirect the output to a text file:
python3 good_roms.py > rom-list.txt
Now that I have a text file with the URLs of all the good ROMs, I can give that file directly to
wget
and it will download just the good ones using the
-i
input file switch:
wget -i rom-list.txt
That’s it! Make sure you have enough space for all the roms and watch them pile up one at a time:
--2019-01-25 21:27:02--  https://rom-site.blah/path/to/roms/YourFavoriteRom[!].bin
Reusing existing connection to [rom-site.blah]:443.
HTTP request sent, awaiting response... 200 OK
Length: 2097152 (2.0M) [application/octet-stream]
Saving to: ‘YourFavoriteRom[!].bin’

YourFavoriteRom[!].bin 100%[========================>]   2.00M   513KB/s    in 3.9s    

2019-01-25 21:27:09 (513 KB/s) - ‘YourFavoriteRom[!].bin’ saved [2097152/2097152]

FINISHED --2019-01-25 21:29:41--
Total wall clock time: 38m 47s
Downloaded: 693 files, 888M in 30m 38s (495 KB/s)

Tags

Comments

More by Andrew Vaillancourt

Topics of interest