title: Python - AttributeError: 'NoneType' object has no attribute 'execute'
body: <p>I am trying to run a python script that logs into Amazon Redshift DB and then execute a SQL command. I use a tool called Airflow for workflow management. When running the below code, I am able to login fine to the DB but when trying to execute the SQL command get the below error.</p>
  
  <pre><code>**AttributeError: 'NoneType' object has no attribute 'execute'**
  </code></pre>
  
  <p><strong>Code:</strong> </p>
  
  <pre><code>## Login to DB
  
  def db_log(**kwargs):
    global db_con
    try:
      db_con = psycopg2.connect(
         " dbname = 'name' user = 'user' password = 'pass' host = 'host' port = '5439'")
    except:
      print("I am unable to connect")
      print('Connection Task Complete')
      task_instance = kwargs['task_instance']
      task_instance.xcom_push(key="dwh_connection" , value = "dwh_connection")
      return (dwh_connection)
  
  
  def insert_data(**kwargs):
    task_instance = kwargs['task_instance']
    db_con_xcom = task_instance.xcom_pull(key="dwh_connection", task_ids='DWH_Connect')
    cur = db_con_xcom
    cur.execute("""insert into tbl_1 select limit 2 ;""")
  </code></pre>
  
  <p>Could anyone help me fix this. Thanks..</p>
  
  <p>Complete code:</p>
  
  <pre><code>## Third party Library Imports
  import pandas as pd
  import psycopg2
  import airflow
  from airflow import DAG
  from airflow.operators.python_operator import PythonOperator
  from airflow.operators.bash_operator import BashOperator
  from datetime import datetime, timedelta
  from sqlalchemy import create_engine
  import io
  
  # Following are defaults which can be overridden later on
  default_args = {
  'owner': 'airflow',
  'depends_on_past': False,
  'start_date': datetime(2018, 5, 29, 12),
  'email': ['airflow@airflow.com']
  }
  
  dag = DAG('sample1', default_args=default_args)
  
  ## Login to DB
  
  def db_log(**kwargs):
    global db_con
    try:
      db_con = psycopg2.connect(
         " dbname = 'name' user = 'user' password = 'pass' host = 'host' port = '5439'")
    except:
      print("I am unable to connect")
      print('Connection Task Complete')
      task_instance = kwargs['task_instance']
      task_instance.xcom_push(key="dwh_connection" , value = "dwh_connection")
      return (dwh_connection)
  
  
  
  t1 = PythonOperator(
    task_id='DWH_Connect',
    python_callable=data_warehouse_login,provide_context=True,
    dag=dag)
  
  #######################
  
  def insert_data(**kwargs):
    task_instance = kwargs['task_instance']
    db_con_xcom = task_instance.xcom_pull(key="dwh_connection", task_ids='DWH_Connect')
    cur = db_con_xcom
    cur.execute("""insert into tbl_1 select limit 2 """)
  
  
  ##########################################
  
  t2 = PythonOperator(
    task_id='DWH_Connect1',
    python_callable=insert_data,provide_context=True,dag=dag)
  
  t1 &gt;&gt; t2
  </code></pre>