main.py

sp = spotipy.Spotify(
    auth_manager=SpotifyOAuth(
        scope="playlist-modify-private",
        redirect_uri="http://example.com",
        client_id=YOUR UNIQUE CLIENT ID,
        client_secret= YOUR UNIQUE CLIENT SECRET,
        show_dialog=True,
        cache_path="token.txt"
    )
)
user_id = sp.current_user()["id"]
date = input("Which year do you want to travel to? Type the date in this format YYYY-MM-DD: ")
song_uris = ["The list of", "song URIs", "you got by", "searching Spotify"]

playlist = sp.user_playlist_create(user=user_id, name=f"{date} Billboard 100", public=False)
# print(playlist)

sp.user_playlist_add_tracks(user=user_id, playlist_id=playlist["id"], tracks=song_uris)

I got this error please help!
spotipy.exceptions.SpotifyException: http status: 403, code:-1 - You cannot create a playlist for another user., reason: None

Had the same error, in: playlist = sp.user_playlist_create(user=user_id, name=f"{date} Billboard 100", public=False) I was using the "client_id" instead of the "user_id", make sure you are not mixing the two as well.

Thank you so much, that was issue.