Python airflow error AttributeError: 'xsensor' object has no attribute 'l'

Question

I am new to Python and airflow. Trying to implement a sensor as below, and the error says "AttributeError: 'mySensor' object has no attribute 'l'" I had a look at other attribute error questions, but I have no idea where the 'l' in my error comes from. Could someone help shed some light on this? Below is the whole class for mySensor. Many thanks.

class mySensor(SFTPSensor):
"""
Subclass of SFTPSensor to override the poke() method 
"""
template_fields = "previous_month"

@apply_defaults
def __init__(self,
             last_day_previous_month,
             *args,
             **kwargs):
    self.previous_month = previous_month
    super(mySensor, self).__init__(*args, **kwargs)

def poke(self, context):
    remote_path = self.path+"file_to_check"+self.previous_month
    file_count = len(self.hook.list_directory(remote_path))
    if file_count == 0:
        return False
    else:
        logging.info("Found %d files", file_count)
        return True

and where I used the Sensor

sensor_task = mySensor(
                    previous_month=_previous_month_template,
                    task_id="check-remote-files",
                    dag=dag,
                    sftp_conn_id=my_conn_id,
                    path="/my/path/"
                    )

can you please format your complete error. It would be helpful to debug. — Underoos
– Underoos, Commented Jul 2, 2019 at 5:10
Can you change template_fields = "previous_month" to template_fields = ["previous_month"]? It is expected to be a list or tuple. Also I don't see last_day_previous_month argument being passed to the sensor but it is an expected argument in __init__ function in your sensor — nightgaunt
– nightgaunt, Commented Jul 2, 2019 at 6:54

BjornO · Accepted Answer · 2019-11-07 11:40:12Z

6

I was getting a similar error with an Airflow operator:

AttributeError: 'MyOperator' object has no attribute 't'

To resolve, check that the template_fields makes sense compared to your __init__ arguments.

You have template_fields = "previous_month" but in your __init__ there is no such parameter.

In my case, the __init__ and template_fields did align. However, I had template_fields = ("myfield") instead of template_fields = ("myfield",). The comma must be present.

answered Nov 7, 2019 at 11:40

BjornO

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2 Comments

phenderbender Over a year ago

wow this is a strange one, thanks for catching the fact that the comma is needed. It is not mentioned nor present in the docs: airflow.apache.org/docs/apache-airflow/1.10.14/howto/…

BjornO Over a year ago

In Python ("xyz") becomes a string, whereas ("xyz",) is a tuple. In BaseOperator the template_fields parameter expects a list / tuple of things to iterate through. Co-incidentally a string is also an iterable of strings which presumably breaks it. An issue has been logged for this - github.com/apache/airflow/issues/12876 Just needs someone to contribute a fix :)

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