content: from builtins import object
  import logging
  import os
  import random
  
  from airflow import settings
  from airflow.models import Connection
  from airflow.utils import AirflowException
  
  CONN_ENV_PREFIX = 'AIRFLOW_CONN_'
  
  
  class BaseHook(object):
      """
      Abstract base class for hooks, hooks are meant as an interface to
      interact with external systems. MySqlHook, HiveHook, PigHook return
      object that can handle the connection and interaction to specific
      instances of these systems, and expose consistent methods to interact
      with them.
      """
      def __init__(self, source):
          pass
  
      @classmethod
      def get_connections(cls, conn_id):
          session = settings.Session()
          db = (
              session.query(Connection)
              .filter(Connection.conn_id == conn_id)
              .all()
          )
          if not db:
              raise AirflowException(
                  "The conn_id `{0}` isn't defined".format(conn_id))
          session.expunge_all()
          session.close()
          return db
  
      @classmethod
      def get_connection(cls, conn_id):
          environment_uri = os.environ.get(CONN_ENV_PREFIX + conn_id.upper())
          conn = None
          if environment_uri:
              conn = Connection(uri=environment_uri)
          else:
              conn = random.choice(cls.get_connections(conn_id))
          if conn.host:
              logging.info("Using connection to: " + conn.host)
          return conn
  
      @classmethod
      def get_hook(cls, conn_id):
          connection = cls.get_connection(conn_id)
          return connection.get_hook()
  
      def get_conn(self):
          raise NotImplemented()
  
      def get_records(self, sql):
          raise NotImplemented()
  
      def get_pandas_df(self, sql):
          raise NotImplemented()
  
      def run(self, sql):
          raise NotImplemented()
  