scraper.py

import collections
import itertools
import praw
import time

# maximum 1000
SUBMISSION_LIMIT = 100

def flatten(it):
    for x in it:
        if (isinstance(x, collections.Iterable) and not isinstance(x, str)):
            for y in flatten(x):
                yield y
        else:
            yield x

reddit = praw.Reddit('submissions/comment scraper by /u/milesrout v0.1.')

subreddit_names = [
    'newzealand',
    'programming'
]

subreddit_authors = {}

# takes iterable of comments, gives those comments and all of their replies
def all_comments_impl(comments):
    return itertools.chain(comments,
                           itertools.chain.from_iterable(
                               all_comments_impl(c.replies) for c in cfilt(comments)))

def cfilt(it):
    return filter(is_comment_with_author, it)

def is_comment_with_author(comm):
    return not isinstance(comm, praw.objects.MoreComments) and comm.author is not None

# takes submission, gives not just top-level comments but ALL comments
def all_comments(submission):
    return cfilt(all_comments_impl(cfilt(submission.comments)))

for j, subname in enumerate(subreddit_names):
    subreddit = reddit.get_subreddit(subname)
    authors = set()
    for i, subm in enumerate(subreddit.get_hot(limit=SUBMISSION_LIMIT)):
        print(100 * float(i + SUBMISSION_LIMIT*j) / (SUBMISSION_LIMIT * len(subreddit_names)) + "%")
        for comm in all_comments(subm):
            if comm.author is not None:
                authors.add(comm.author.name)
    subreddit_authors[subname] = authors

print set.intersection(*(subreddit_authors[k] for k in subreddit_authors))