http://chriskief.com/2014/11/05/google-analytics-api-using-python-and-a-service-account/

google.py

import httplib2

from googleapiclient.discovery import build
from googleapiclient.http import HttpError
from oauth2client.client import SignedJwtAssertionCredentials

def get_metrics():

    # load the service account key
    # this key is managed here - https://console.developers.google.com/project
    filename = 'YOUR-KEY-FILE.p12'
    f = file(filename, 'rb')
    key = f.read()
    f.close()

    # create the credentials
    credentials = SignedJwtAssertionCredentials('[email protected]', key, scope='https://www.googleapis.com/auth/analytics.readonly')

    # authorize the http instance with these credentials
    http = httplib2.Http()
    http = credentials.authorize(http)

    # construct a resource object for interacting with an api
    service = build('analytics', 'v3', http=http)

    # build the query
    # your profile id can be found by heading to google analytics, selecting your profile, clicking the admin button, 
    # and then clicking view settings under the view column, the id is labelled 'View ID'
    # you can see the available metrics here:
    # https://developers.google.com/analytics/devguides/reporting/core/dimsmets
    api_query = service.data().ga().get(
        ids='ga:YOUR_PROFILE_ID_NOT_UA',
        metrics='ga:users, ga:sessions, ga:avgSessionDuration, ga:pageviews, ga:pageviewsPerSession, ga:percentNewSessions, ga:bounceRate',
        start_date='2014-01-01',
        end_date='2015-01-01'
    )

    # default value
    metrics = None

    # run it
    try:
        result = api_query.execute()
        values = result['rows'][0]

        # covert the average session to minutes and seconds
        minutes, seconds = divmod(int(float(values[2])), 60)

        # the order below is the same as the order the metrics were listed above
        metrics = {
            'users': values[0],
            'sessions': values[1],
            'avg_session': '%d:%02d' % (minutes, seconds),
            'pageviews': values[3],
            'pages_session': '%.2f' % float(values[4]),
            'new_sessions': '%.2f' % float(values[5]) + '%',
            'returning_sessions': '%.2f' % (100 - float(values[5])) + '%',
            'bounce_rate': '%.2f' % float(values[6]) + '%'
        }

    # handle errors in constructing a query
    except TypeError, error:
        print ('There was an error in constructing your query : %s' % error)

    # handle api service errors
    except HttpError, error:
        print ('There was an API error : %s : %s' % (error.resp.status, error._get_reason()))

    return metrics