You need to create/register the app with reddit, and you'll get an id and secret from them to use in your script. Here's a guide (with a link to a quickstart guide if that's more your fancy): https://github.com/reddit/reddit/wiki/OAuth2

The error is caused from a missing client_id (which is your unique API key and secret for the Reddit API) in your praw.ini file or in your Python script.

In your script you could have something like:

r.set_oauth_app_info(client_id='stJlUSUbPQe5lQ',
...                      client_secret='DoNotSHAREWithANYBODY',
...                      redirect_uri='http://127.0.0.1:65010/'
...                                   'authorize_callback')

https://praw.readthedocs.io/en/stable/pages/oauth.html?highlight=client_id#step-2-setting-up-praw

Or set up in the praw.ini file as described in the link below:

https://praw.readthedocs.io/en/stable/pages/configuration_files.html#configuration-variables

If you have already signed up for access to the reddit API, it says:

https://www.reddit.com/wiki/api

OAUTH Client ID(s) *

• if you don't have yet, please email [email protected] when received or when you add additional

You can get your client_id from your app in: https://www.reddit.com/prefs/apps

In this example from their documentation (under the API app title): the client_id=p-jcoLKBynTLew

[Promoted/expanded from a comment]

As pointed out by @bboe, the PRAW docs can be located here ¹.

Specifically, you want the Getting Started ¹ page which walks you through instantiating a Reddit object in read-only or read/write mode.

¹ PRAW 4 documentation is no longer available onlne, so I've updated the links to track the latest version.