lfmh 1.1.1

A Last.fm API interface.

Features

• Supports all packages and methods listed at http://www.last.fm/api.

• Methods return plain Python types: dictionaries and lists.

• If the user wishes, the library can make an application comply to the point 4.4 of Last.fm’s API ToS, which says that the request rate of an application must be limited.

• Handles all Last.fm API errors via exceptions.

• Easily extendible.

A tutorial

A short introduction

lfm.App

Instantiate a Last.fm application:

from lastfm import lfm

app = lfm.App(API_KEY, SECRET)

The above is self-explanatory. You’ll need an API key and the corresponding “secret” given by Last.fm. If you don’t have those handy, you can ommit them for testing purposes, as lfm comes with its own. You are expected to provide your own key and secret in real applications.

If you want your application to comply to Last.fm’s request rate limit, you’ll need to provide a third argument, a file in which a sqlite3 database which tracks requests will be stored.

LFM_FILE = "lfm.dat"

app = lfm.App(API_KEY, SECRET, LFM_FILE)

As a fourth argument, you can provide a tuple of your program’s name and version, to be used in the user-agent:

NAME    = "myprogram"
VERSION = "1.0.0"

app = lfm.App(API_KEY, SECRET, LFM_FILE, (NAME, VERSION))

The user-agent is formatted as “NAME/VERSION lfm/LFMVERSION”. If you don’t provide this information, both the name and version will be “unknown”.

Methods and packages

API methods are organized like so:

data = app.package.method_name(...)

So, if you wanted to, for example, fetch all recently listened tracks of a user, you’d do something like this:

tracks = app.user.get_recent_tracks(user)

Note the underscores. Last.fm uses camelCase for method names. Such a thing isn’t Pythonic, though, hence the transformation of names to under_scores.

Authenticating

auth.get_mobile_session()

Let’s get a user’s session now. There are three ways to do this. The first one is by supplying a username and a password:

session = app.auth.get_mobile_session(user, pwd)

auth.get_session()

The second one is more complicated, but more secure and trustworthy. First, you need to fetch a token:

token = app.auth.get_token()

Then you have to make the user authenticate the token by pointing him to the authentication web-page:

import webbrowser

webbrowser.open(token.url)
input("Press enter after granting access.")

After the user has granted access, all that’s left is to fetch the session:

session = app.auth.get_session(token)

auth.get_url()

The third one is for web apps. auth.get_url() takes one argument, a callback URL, and returns an URL which points to the authentication page. When the user authenticates, the page redirects to the callback URL with the token appended as a GET parameter. For more information, consult the official Last.fm documentation.

Using the session

Regardless of which of the methods you use, a session needs to be bound to your app by assigning the session key to the App’s session_key attribute:

app.session_key = session["key"]

That’s all. You can now call methods which require authentication:

app.track.remove_tag(artist, track, tag)

More

For more information on specific methods, consult the API page on Last.fm.

An advanced tutorial

Custom requests

Say, for example, that Last.fm has added a new method not yet available in this library. What can be done then? The solution is actually quite straightforward: use App.request(). You can manually specify the API package, method and parameters:

def playlist_remove(app, playlist_id):
    params = {
              "playlistID": playlist_id,
             }

    return app.request("playlist", "remove", params)

Simple as that.

Adding new packages

App.request_auto()

What if, by some miracle, a whole new package with a bunch of methods was added? You’d want to use those methods several times in your program. Calling request() every time would be quite cumbersome; very repetitive and error-prone.

Well, an unlikely hero arises: App.request_auto()! This function tries to automate every bit of requesting that can possibly be automated, and generally succeeds very well! This whole library is built on that one function. Here’s an example from the source itself:

class Track(Package):

    ...

    def get_info(self, artist = None, track = None, username = None, autocorrect = None, mbid = None):
        data = self.app.request_auto()
        return data["track"]

    ...

What kind of magick is this? Well, without going into too much detail (open source, remember?), the function cleverly learns all of the three, if possible: the package, the method, the parameters:

• It assembles the method name from the caller function’s name; “getInfo” in this case.

• The parameters, ignoring self, are grabbed from the caller’s arguments. Parameter names are stripped of trailing underscores, to allow the use of parameters such as from. True to the Python’s philosophy of “duck-tape” programming, the function tries to accept all kinds of types as parameters. It handles all primitive ones well: integers, floats, booleans, and such. Of the more complicated types, it can handle lists, but not dictionaries.

• The name of the package is learned from the name of the class the function’s in, but only if the class inherits lfm.Package.

request_auto() is not only intelligent and elegant, it’s also flexible. You can override any of the three:

def get_info(self, artist = None, track = None, username = None, autocorrect = None, mbid = None):
    package = "the_correct_package_name"
    method  = "the_correct_method_name"

    params  = {
               "special" : 0xDEADBEEF,
               "mbid"    : None,
              }

    data = self.app.request_auto(package, method, params)
    return data["track"]

So, we have added a new parameter called special, and made mbid always None, whatever the user may have passed. Pretty neat, huh? Note that params will be merged into the auto-gathered dictionary of parameters, not overwrite them.

Inheriting Package

Very well, your custom-made Package would look something like this:

class Forum(Package):
    def post(self, threadid, msg):
        data = self.app.request_auto()
        return data

And you’d use it like so:

forum = Forum(app)
forum.post("1832723", "Hello folks!")

Inheriting App

To add the finishing touch, you could extend App:

class App(lfm.App):
    forum = None

    def __init__(self, key, secret, db = None, info = None):
        super().__init__(key, secret, db, info)

        forum = Forum(self)

And with that:

app.forum.post("1832723", "Hello folks!")