Reddit Subreddit Completion

subreddit_complete.py

import sys
import uuid
import re
import json
import urllib.request
import urllib.parse

subreddit_rx = re.compile(r'\A[A-Za-z0-9][A-Za-z0-9_]{,20}\Z')
subreddit_url = 'https://www.reddit.com/api/search_reddit_names.json'


def is_valid_subreddit_prefix(prefix: str) -> bool:
    return re.match(subreddit_rx, prefix) is not None


def subreddit_search(prefix: str) -> [str]:
    if not is_valid_subreddit_prefix(prefix):
        raise Exception('Invalid subreddit name: {}'.format(prefix))

    post_data = urllib.parse.urlencode({
        'query': prefix,
        'include_over_18': 'true',
        'renderstyle': 'html',
    }).encode('ascii')

    opener = urllib.request.build_opener()
    opener.addheaders = [('User-Agent', 'Search-Subreddits-Python-' +
                          str(uuid.uuid4()))]

    with opener.open(subreddit_url, post_data) as f:
        data = f.read().decode('utf-8')
    data = json.loads(data)
    return data['names']


if __name__ == '__main__':
    import os

    if len(sys.argv) != 2:
        print('Usage: {} {} SUBREDDIT_PREFIX'.format(
            os.path.split(sys.executable)[-1],
            sys.argv[0],
        ))
        sys.exit(-1)

    try:
        names = subreddit_search(sys.argv[1])
    except Exception as ex:
        print(ex)
        sys.exit(-1)

    if len(names) == 0:
        print('{}: No subreddit matches'.format(sys.argv[1]))
    else:
        print(sys.argv[1] + ':')
        for sr in names:
            print((' ' * 4) + sr)