Add initial code.

Procfile

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+bot: python bot.py

bot.py

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+import praw
+import requests
+import bs4
+import html2text
+import time
+
+
+USERNAME = 'arXiv_abstract_bot'
+PASSWORD = '********'
+CLIENT_ID = '*******'
+SECRET = '********'
+
+r = praw.Reddit(
+    username=USERNAME,
+    password=PASSWORD,
+    client_id=CLIENT_ID,
+    client_secret=SECRET,
+    user_agent='linux:arXiv_abstract_bot:0.2 (by /u/arXiv_abstract_bot'
+    )
+
+subreddit = r.subreddit('machinelearning')
+
+alreadydone = set()
+
+def scrape_arxiv(url):
+    r = requests.get(url)
+    soup = bs4.BeautifulSoup(r.text)
+    abstract = soup.select('.abstract')[0]
+    abstract = html2text.html2text(abstract.decode()).replace('\n', ' ')
+
+    authors = soup.select('.authors')[0]
+    authors = html2text.html2text(authors.decode()).replace('\n', ' ')
+    authors = authors.replace('(/', '(http://arxiv.org/')
+
+    title = soup.select('.title')[0]
+    title =  html2text.html2text(title.decode()).replace('\n', ' ')[2:]
+
+    abs_link = u'[Landing page]({})'.format(url)
+    pdf_url = url.replace('/abs/', '/pdf/')
+    pdf_link = u'[PDF link]({})'.format(pdf_url)
+    links = u'{}  {}'.format(pdf_link, abs_link)
+    response = '\n\n'.join([title, authors, abstract, links]) 
+    return response
+
+
+def comment():
+    print(time.asctime(), "searching")
+    try:
+        all_posts = subreddit.new(limit=100)
+        for post in all_posts:
+            if 'arxiv.org' in post.url:
+                if post.id in alreadydone:
+                    continue
+                for comment in post.comments:
+                    if str(comment.author) == USERNAME:
+                        break
+                else:
+                    landing_url = post.url
+                    if '.pdf' in landing_url:
+                        landing_url = post.url.replace('.pdf', '')
+                        landing_url = landing_url.replace('/pdf/', '/abs/')
+
+                    response = scrape_arxiv(landing_url)
+                    post.reply(response)
+                    alreadydone.add(post.id)
+                    print(landing_url, response)
+                    time.sleep(10)
+    except Exception as error:
+        print(error)
+
+
+if __name__ == "__main__":
+    while True:
+        comment()
+        time.sleep(30)