Username Scrape

import praw

#Reddit instance
reddit = praw.Reddit(client_id='XXXXXXXXXXXX',
                    client_secret='XXXXXXXXXXXX',
                    password='XXXXXXXXXXXXX',
                    user_agent='UNameCollectorStudy',
                    username='gcf16')

#Request user enter session ID
sub_name = input('Which Sub are we looking at today?  >')
with open ('output.csv', 'a') as f:
    f.write('Today\'s Date and Time on ' + sub_name)
    f.write('\n')
    f.write('\n')

x = 0
while x == 0:
    session_id = input('Enter session ID   >')

# Fetch thread contents where submission_id is found
    thread = reddit.submission(id=session_id)

#create list to store usernames
    authors = []

#Add authors to CSV
    with open ('output.csv', 'a') as f:
        for each in thread.comments.list():
            authors.append(each.author)
            f.write(str(each.author))
            f.write('\n')