First Steps into the Quantified Self: Getting to Know the Fitbit API

Today I have been experimenting with the Fitbit API.

Here are some rather amateurish steps for getting data from Fitbit’s “cloud”.

Simple Client Setup for Public Data

1. Get and setup a Fitbit product.

I have access to a set of Fitbit scales (the “Aria”). The Fitbit Force looks quite good; I may get one of those when they are launched in the UK to record steps.

2. Register an “App”

Goto https://dev.fitbit.com. Login using your Fitbit password from 1). Click the link to add an “app”.

3. Setup Libraries

Install oauth2:

sudo pip install oauth2

Clone python-fitbit:

mkdir Healthcare
cd Healthcare
git clone https://github.com/orcasgit/python-fitbit.git

4. Record Consumer Key & Secret

After registering your “app” in 2) above, you have access to a “Consumer Key” and a “Consumer Secret”. You can access these details by going to “Manage My Apps”. I then store these in a “config.ini” file I keep in my working project directory. For example:

[Login Parameters]
C_KEY=*key_string*
C_SECRET=*secret_string*

5. Access Public Data

With the client variables we can access public data on Fitbit.

import fitbit
import ConfigParser

#Load Settings
parser = ConfigParser.SafeConfigParser()
parser.read('config.ini')
consumer_key = parser.get('Login Parameters', 'C_KEY')
consumer_secret = parser.get('Login Parameters', 'C_SECRET')

#Setup an unauthorised client (e.g. with no user)
unauth_client = fitbit.Fitbit(consumer_key, consumer_secret)

#Get data for a user
user_params = unauth_client.user_profile_get(user_id='1ABCDE')

You can get your user ID by accessing your Fitbit profile page. It is displayed in a URL just above any photo you may have. The last command returns a JSON string similar to this one:

{u'user': {u'city': u'', u'strideLengthWalking': 0, u'displayName': u'USERNAME', u'weight': 121.5, u'country': u'', u'aboutMe': u'', u'strideLengthRunning': 0, u'height': 0, u'timezone': u'UTC', u'dateOfBirth': u'', u'state': u'', u'encodedId': u'1ABCDE', u'avatar': u'https://pic_url.jpg', u'gender': u'NA', u'offsetFromUTCMillis': 0, u'fullName': u'', u'nickname': u'', u'avatar150': u'https://pic_url.jpg'}}

As I am only looking at getting a current weight reading (as taken from the last Aria scales measurement) I could stop here, as long as I have made my “body” data public (viewable by “Anyone” on the Fitbit profile > privacy page). However, as I wanted to get a BMI and body fat reading I continued with user authentication.

User Authenication

The python-fitbit library has a routine called gather_keys_cli.py. I followed this routine in iPython to get the user key and secret for my own Fitbit account.

1. Fetch Request Token

client = fitbit.FitbitOauthClient(consumer_key, consumer_secret)
token = client.fetch_request_token()
print 'FROM RESPONSE'
print 'key: %s' % str(token.key)
print 'secret: %s' % str(token.secret)
print 'callback confirmed? %s' % str(token.callback_confirmed)
print ''

2. Allow Access to User Fitbit Account

I first followed the steps:

print '* Authorize the request token in your browser'
print ''
print 'open: %s' % client.authorize_token_url(token)
print ''

I had registered my callback URL as http://localhost/callback. I had not actually implemented a request handler for this URL on my local machine. However, I learnt this was not a problem – the parameters I needed were included in the callback URL. Even though the page got a ‘404’ I could still see and extract the ‘verifier’ parameter from the URL in the browser.

3. Get User Key and Secret

First I stored the ‘verifier’ parameter from the URL as a string (verifier = “*parameterfromURL*”). Then I ran these steps to get the user key and secret:

print '* Obtain an access token ...'
print ''
print 'REQUEST (via headers)'
print ''
token = client.fetch_access_token(token, verifier)
print 'FROM RESPONSE'
print 'key: %s' % str(token.key)
print 'secret: %s' % str(token.secret)
print ''

4. Save User Key and Secret and Use in Request

The last step is to save the user key and secret in the “config.ini” file. I saved these as “U_KEY” and “U_SECRET” in a similar manner to the consumer key and secret. Hence, these variables could be retrieved by calling:

user_key = parser.get('Login Parameters', 'U_KEY')
user_secret = parser.get('Login Parameters', 'U_SECRET')

Finally, we can use both sets of keys and secrets to access the more detailed user data:

authd_client = fitbit.Fitbit(consumer_key, consumer_secret, user_key=user_key, user_secret=user_secret)

body_stats = authd_client._COLLECTION_RESOURCE('body')

Todo

Some further work includes:

• Adapting the python-fitbit routines for the iHealth API.
• Building a script that gets data and imports into a website datastore.
• Using the body data to alter a SVG likeness.