Ad Exchange Buyer API v1 code samples.

Reviewed in http://codereview.appspot.com/5711045/.

Index: samples/adexchangebuyer/client_secrets.json
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diff --git a/samples/adexchangebuyer/sample_utils.py b/samples/adexchangebuyer/sample_utils.py
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+#!/usr/bin/python
+#
+# Copyright 2012 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Auxiliary file for Ad Exchange Buyer API code samples.
+
+Handles various tasks to do with logging, authentication and initialization.
+"""
+
+__author__ = 'david.t@google.com (David Torres)'
+
+import logging
+import os
+import sys
+from apiclient.discovery import build
+import gflags
+import httplib2
+from oauth2client.client import flow_from_clientsecrets
+from oauth2client.file import Storage
+from oauth2client.tools import run
+
+
+FLAGS = gflags.FLAGS
+
+# CLIENT_SECRETS, name of a file containing the OAuth 2.0 information for this
+# application, including client_id and client_secret, which are found
+# on the API Access tab on the Google APIs
+# Console <http://code.google.com/apis/console>
+CLIENT_SECRETS = 'client_secrets.json'
+
+# Helpful message to display in the browser if the CLIENT_SECRETS file
+# is missing.
+MISSING_CLIENT_SECRETS_MESSAGE = """
+WARNING: Please configure OAuth 2.0
+
+To make this sample run you will need to populate the client_secrets.json file
+found at:
+
+   %s
+
+with information from the APIs Console <https://code.google.com/apis/console>.
+
+""" % os.path.join(os.path.dirname(__file__), CLIENT_SECRETS)
+
+# Set up a Flow object to be used if we need to authenticate.
+FLOW = flow_from_clientsecrets(
+    CLIENT_SECRETS,
+    scope='https://www.googleapis.com/auth/adexchange.buyer',
+    message=MISSING_CLIENT_SECRETS_MESSAGE
+    )
+
+# The gflags module makes defining command-line options easy for applications.
+# Run this program with the '--help' argument to see all the flags that it
+# understands.
+gflags.DEFINE_enum('logging_level', 'ERROR',
+                   ['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'],
+                   'Set the level of logging detail.')
+
+
+def process_flags(argv):
+  """Uses the command-line flags to set the logging level."""
+
+  # Let the gflags module process the command-line arguments.
+  try:
+    argv = FLAGS(argv)
+  except gflags.FlagsError, e:
+    print '%s\nUsage: %s ARGS\n%s' % (e, argv[0], FLAGS)
+    sys.exit(1)
+
+  # Set the logging according to the command-line flag.
+  logging.getLogger().setLevel(getattr(logging, FLAGS.logging_level))
+
+
+def initialize_service():
+  """Initializes and returns an instance of the Ad Exchange Buyer service.
+
+  Authorizes the user for use of the service and returns it backs.
+
+  Returns:
+      The authorized and initialized service.
+  """
+
+  # Create an httplib2.Http object to handle our HTTP requests.
+  http = httplib2.Http()
+
+  # Prepare credentials, and authorize HTTP object with them.
+  # If the credentials don't exist or are invalid run through the native client
+  # flow. The Storage object will ensure that if successful the good
+  # credentials will get written back to a file.
+  storage = Storage('adexchangebuyer.dat')
+  credentials = storage.get()
+  if credentials is None or credentials.invalid:
+    credentials = run(FLOW, storage)
+  http = credentials.authorize(http)
+
+  # Construct a service object via the discovery service.
+  service = build('adexchangebuyer', 'v1', http=http)
+  return service
+