'NoneType' object 没有属性'光标' airflow

Question

I am trying to test Apache Airflow with basic 3 function. And assigning them to 3 tasks in the same order. But there is problem that:

When I am trying to load the data to POstgresql db it is throwing error that NoneType object with no attribute cursor

Any suggestions how I can solve it?

The code is:

def fetch_data():

    global df
    #Fetch data from url
    url = 'http://api.open-notify.org/astros.json'
    response = requests.get(url)

    logging.info(response.status_code)
    json_data = response.json()
    logging.info(json_data)

    #Normalize it
    df = json_normalize(json_data['people'])
    return df

def connect_to_db():
    global engine
    # Connect to database (Note: The package psychopg2 is required for Postgres to work with SQLAlchemy)
    engine = create_engine("postgresql://postgres:postgres@localhost/postgres")
    logging.info('Connected to the database')

    # Verify that there are no existing tables
    print(engine.table_names())
    return engine

def load_data():
    engine = connect_to_db()
    df = fetch_data()
    table_name = 'astro'
    logging.info('Table is created')
    df.to_sql(table_name, engine)
    logging.info('Data is loaded.')

Traceback:

ERROR - 'NoneType' object has no attribute 'cursor'
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/airflow/models/taskinstance.py", line 926, in _run_raw_task
    result = task_copy.execute(context=context)
  File "/usr/local/lib/python2.7/dist-packages/airflow/operators/python_operator.py", line 113, in execute
    return_value = self.execute_callable()
  File "/usr/local/lib/python2.7/dist-packages/airflow/operators/python_operator.py", line 118, in execute_callable
    return self.python_callable(*self.op_args, **self.op_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/airflow/example_dags/sample_task.py", line 65, in load_data
    df.to_sql(name=table_name, con = engine, if_exists='append')
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/generic.py", line 2531, in to_sql
    dtype=dtype, method=method)
  File "/usr/local/lib/python2.7/dist-packages/pandas/io/sql.py", line 460, in to_sql
    chunksize=chunksize, dtype=dtype, method=method)
  File "/usr/local/lib/python2.7/dist-packages/pandas/io/sql.py", line 1546, in to_sql
    table.create()
  File "/usr/local/lib/python2.7/dist-packages/pandas/io/sql.py", line 572, in create
    if self.exists():
  File "/usr/local/lib/python2.7/dist-packages/pandas/io/sql.py", line 560, in exists
    return self.pd_sql.has_table(self.name, self.schema)
  File "/usr/local/lib/python2.7/dist-packages/pandas/io/sql.py", line 1558, in has_table
    return len(self.execute(query, [name, ]).fetchall()) > 0
  File "/usr/local/lib/python2.7/dist-packages/pandas/io/sql.py", line 1426, in execute
    cur = self.con.cursor()
AttributeError: 'NoneType' object has no attribute 'cursor'

Answer 1

I have removed the global variable and kept rest same and it worked.

Thanks, people!