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Mastodon: How To List Followed Hashtags

December 21, 2022

Mastodon recently introduced hashtags, but does not yet have a user interface for listing which hashtags you follow. Since there is an extensive API, I thought it would be straightforward to grab the list that way—and, it is, but you need to perform the authorization dance correctly!

Query steps #

To access the Mastodon API, you first register an application. You can choose any appropriate name for your app; here I use ls_hashtag.
The application can make public queries, but to access personal information must first be granted access by the user.
Once the user authorizes the app, an oauth token can be obtained.
This token, in turn, allows personal API access.

Implementation #

Without further ado, some Python code which implements the above. It caches secrets in ~/.config/mastodon-tags.yaml. I suspect tokens expire after a while, but the script doesn’t yet take that into account.

#!/usr/bin/env python

import requests
import yaml
import os
import webbrowser
import sys


SERVER = 'https://your.mastodon.server'
APP_NAME = 'ls_hashtag'
CONFIG = os.path.expandvars('$HOME/.config/mastodon-tags.yaml')


def get_config():
    if os.path.isfile(CONFIG):
        config = yaml.load(open(CONFIG, 'r'), Loader=yaml.SafeLoader) or {}
    else:
        config = {}
    return config


def update_config(update_dict):
    cfg = get_config()
    cfg = {**update_dict, **cfg}
    with open(CONFIG, 'w') as f:
        yaml.dump(cfg, f)
    return cfg


def post(url, **kwargs):
    data = requests.post(url, **kwargs).json()
    if 'error' in data:
        print(f'POST {url}')
        print()
        print(json['error'])
        sys.exit(1)
    return data


cfg = get_config()


if not 'client_id' in cfg:
    data = post(
        f'{SERVER}/api/v1/apps',
        json={
            'client_name': APP_NAME,
            'redirect_uris': 'urn:ietf:wg:oauth:2.0:oob',
            'scopes': 'read'
        }
    )
    cfg = update_config({
        'client_id': data['client_id'],
        'client_secret': data['client_secret']
    })


if not 'authorization_code' in cfg:
    oauth_url = f"{SERVER}/oauth/authorize?client_id={cfg['client_id']}&client_secret={cfg['client_secret']}&response_type=code&redirect_uri=urn:ietf:wg:oauth:2.0:oob"
    webbrowser.open(oauth_url)

    auth_code = input("Enter token from browser window: ")
    cfg = update_config({
        'authorization_code': auth_code
    })


# Obtain OAuth access token
if not 'access_token' in cfg:
    data = post(
        f'{SERVER}/oauth/token',
        json={
            "grant_type": "authorization_code",
            "code": cfg['authorization_code'],
            "client_id": cfg['client_id'],
            "client_secret": cfg['client_secret'],
            "redirect_uri": "urn:ietf:wg:oauth:2.0:oob"
        }
    )
    cfg = update_config({
        'access_token': data['access_token']
    })

data = requests.get(
    f'{SERVER}/api/v1/followed_tags',
    headers={'Authorization': f"Bearer {cfg['access_token']}"}
).json()

N = max(len(tag['name']) for tag in data)
for hashtag in data:
    print(f'#{hashtag["name"]:{N}} {hashtag["url"]}')

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