Getting Started

Getting Started

In this turorial we'll go over everything needed to create a bot or program using reddit's API through the Python Reddit API Wrapper (PRAW). We're going to write a program that breaks down a redditor's karma by subreddit, just like the reddit gold feature. Unlike that, our program can break it down for any redditor, not just us. However, it will be less precise due to limitations in the reddit API, but we're getting ahead of ourselves.

This is a beginners tutorial to the PRAW. We'll go over the hows and whys of everything from getting started to writing your first program accessing reddit. What we won't go over in this tutorial is the Python code.

Connecting to Reddit

Start by firering up Python and importing the PRAW as a module. You can find the module and installation instructions in the python module description.

import praw

Next we need to connect to reddit and identify our script. We do this through the user_agent we supply when our script first connects to reddit.

user_agent = "Karma breakdown 1.0 by /u/_Daimon_ github.com/AndreasDamgaardPedersen/Reddit-Bots/"
r = praw.Reddit(user_agent=user_agent)

Care should be taken when we decide on what user_agent to send to reddit. The user_agent field is how we uniquely identify our script. The reddit API wiki page has the official and updated recommendations on user_agent strings and everything else. Reading it is highly recommended. Here's the part about user_agent recommendations included for the sake of completion.

---

• Change your client's User-Agent string to something unique and descriptive, preferably referencing your reddit username.
• Example: User-Agent: super happy flair bot by /u/spladug
• Many default User-Agents (like "Python/urllib" or "Java") are drastically limited to encourage unique and descriptive user-agent strings.
• NEVER lie about your user-agent. This includes spoofing popular browsers and spoofing other bots. We will ban liars with extreme prejudice.

---

In addition to reddit's recommendations, it's often nice to to add a version number and a link to the script's source (if available).

Breaking down Redditor Karma by Subreddit

Now that we've established contact with reddit, it's time for the next step in our script to break down a user's karma by subreddit. There isn't a function that does this, but luckily it's fairly easy to write the python code to do this ourselves.

We use the function get_redditor to get a Redditor instance that represents a user on reddit. In the following case user will provide access to the reddit user _Daimon_.

user_name = "_Daimon_"
user = r.get_redditor(user_name)

Next we can use the functions get_comment and get_submitted to get that redditor's comments and submissions. Both are a part of the superclass Thing as mentioned on the reddit API wiki page. Both functions can be called with the parameter limit, which limits how many things we receive. As a default, PRAW makes calls to reddit with limit=25. The default can be edited in the module's configuration files. When the limit is set to None, PRAW will try to retrieve all the things. However, due to limitations in the reddit API (not PRAW) we might not get all the things, but more about that later. During development you should be nice and set the limit lower to reduce reddit's workload, if you don't actually need all the results.

thing_limit = 10
gen = user.get_submitted(limit=thing_limit)

Next we take the generator containing things (either comments or submissions) and iterate through them to create a dictionary with the subreddit display names (e.g. python and proper) as keys and the karma obtained in those subreddits as values.

karma_by_subreddit = {}
for thing in gen:
   subreddit = thing.subreddit.display_name
   karma_by_subreddit[subreddit] = (karma_by_subreddit.get(subreddit, 0) 
                                   + thing.score)

And we're done. The program could use a way of displaying the data, exception catching, etc. If you're interested, you can check out my more fleshed out version of this Karma-Breakdown program.

Obfuscation and API limitations

As I mentioned before there are limits in reddit's API. There is a limit to the amount of things reddit will return before it barfs. Any single reddit listing will display at most 1000 items. This is true for all listings including subreddit submission listings, user submission listings, and user comment listings.

You may also have realised that the karma values change from run to run. This inconsistency is due to reddit's obfuscation of the upvotes and downvotes. The obfuscation is done to everything and everybody to thwart potential cheaters. There's nothing we can do to prevent this.

Another thing you will probably have noticed is that retrieving a lot of elements take a lot of time. Our requests are broken into pieces of 25 things by PRAW, and then sent sequentially to reddit. But they are separated by a delay of 2 seconds, to follow the guidelines in the reddit API wiki page. Therefore retrieving 100 things, will cost 2x4=8 seconds to API delay.