The repl.it database

Database commands

There's a simple key:value store associated with every repl. To work with it in Python, we first import the db module from replit:

from replit import db

Then, we can:

• Set values: db['my_key'] = my_value
• Get values: my_variable = db['my_key']
• Delete entries: del db['my_key']
• List the keys: list(db.keys())
• Clear the database: db.clear()

repl.it code snippet

Code walkthrough

from auth import access_token

• we've imported access_token from auth.py (in which we copied our own token), and can now use access_token in our subequent code

from replit import db

• we've imported the db module from replit so we can use its methods to work with the database

from tracks import get_track_data, track_summary

• we've imported some functions from tracks.py which we'll use later

db.clear()

• the .clear() method will remove all content (keys and values) from the database
  • remove or comment out this line if you want to re-run main.py without doing so...

track_id = '2H7PHVdQ3mXqEHXcvclTB0' #'7azo4rpSUh8nXgtonC6Pkq'
track_data = get_track_data(access_token, track_id)

• we assign a value to track_id (the commented out one is an alternative for you to try), and then call the get_track_data() function, using access_token and track_id as arguments, assigning the result to track_data

get_track_data() function

Take a look at tracks.py; you'll see the function definitions for the two functions we imported from there into main.py.

• get_track_data() will attempt to collect the track data from the Spotify API as we have seen previously, using the access_token and track_id supplied to it

  • if successful, track_data in main.py will hold the returned data
  • if not, an error will be printed and the track_data value will be None

Writing to the database

if track_data:
    db[track_id] = track_data

• if the track_data value is 'truthy' (by this we mean not empty, zero, False or None), the following line will be executed, and track_data will be written to the database, as the value associated with the key of track_id
• if get_track_data() returned None, track_data would therefore be None, and the line underneath the if statement will be skipped

Reading from the database

print(list(db.keys()))

print(track_summary(db[track_id]))

• we used the .keys() method to fetch a list of the database keys; the object returned by this method is an iterable, on which we need to use the Python built-in list() function to get the keys themselves

• we called the track_summary() function, using the value from the database associated with the key equal to track_id, i.e. the data previously fetched from the API and stored there

  • this function would throw an error if the key isn't in the database
  • we print() the value returned by track_summary() function

track_summary() function

We can see what track_summary() will do by looking at the code in tracks.py:

summary = {
        'track_name': track_data['name'],
        'artist_name': track_data['artists'][0]['name'],
        'album_name': track_data['album']['name'],
        'image_url': track_data['album']['images'][0]['url'],
    }

• the function extracts specific features nested in track_data (which contained everything in the response sent by the Spotify API to our request for the given track), and returns a dictionary

We could have extracted these features before writing to the database and then only storing this smaller dataset - but by storing all of the data from the API response, we could change which features we want to use later on, without having to make another request to the API.