old_contents: # Copyright 2019 Google LLC
  #
  # 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
  #
  #     https://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.
  
  import os
  
  
  def main():
      key_path = os.environ.get("GOOGLE_APPLICATION_CREDENTIALS")
  
      # [START bigquery_client_json_credentials]
      from google.cloud import bigquery
      from google.oauth2 import service_account
  
      # TODO(developer): Set key_path to the path to the service account key
      #                  file.
      # key_path = "path/to/service_account.json"
  
      credentials = service_account.Credentials.from_service_account_file(
          key_path, scopes=["https://www.googleapis.com/auth/cloud-platform"],
      )
  
      client = bigquery.Client(credentials=credentials, project=credentials.project_id,)
      # [END bigquery_client_json_credentials]
      return client
  
  
  if __name__ == "__main__":
      main()
  
new_contents: # Copyright 2019 Google LLC
  #
  # 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
  #
  #     https://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.
  
  import os
  
  
  def main():
      key_path = os.environ.get("GOOGLE_APPLICATION_CREDENTIALS")
  
      # [START bigquery_client_json_credentials]
      from google.cloud import bigquery
      from google.oauth2 import service_account
  
      # TODO(developer): Set key_path to the path to the service account key
      #                  file.
      # key_path = "path/to/service_account.json"
  
      credentials = service_account.Credentials.from_service_account_file(
          key_path, scopes=["https://www.googleapis.com/auth/cloud-platform"],
      )
  
      # Alternatively, use service_account.Credentials.from_service_account_info()
      # to set credentials directly via a json object rather than set a filepath
      # TODO(developer): Set key_json to the content of the service account key file.
      # credentials = service_account.Credentials.from_service_account_info(key_json)
  
      client = bigquery.Client(credentials=credentials, project=credentials.project_id,)
      # [END bigquery_client_json_credentials]
      return client
  
  
  if __name__ == "__main__":
      main()
  
subject: Add alternative approach to setting credentials (#517)