Undefined Variable 'self' when attempting Object Orientated python script-CodePudding

I'm trying to build a program that automatically creates our batch pipelines from MySQL to BigQuery and I'm randomly getting this linting error: "Undefined Variable 'self'".

The DESTINATION_TABLE_FORMAT class constant is not able to access self.environment() as it is giving the undefined variable self error.

When I move data_lake_paths by one indentation inwards, it starts to work but I'm no longer able to access it by calling the variable.

Any help would be much appreciated


class MySQLBatchPipeline:
    '''
    Class to generate MySQL batch pipelines that store CSV's
    in GCS then import them into BigQuery
    '''
    export_format='CSV'
    DESTINATION_TABLE_FORMAT = self.get_environment()   '.{dataset}.{table}' #<- linter flags this as "Undefined Variable 'self'"
    def __init__(
        self,
        dag,
        sql_directory,
        gcp_project_id,
        mysql_connection_id,
        source_schema,
        source_table,
        gcs_connection_id,
        bq_connection_id,
        gcs_bucket,
        destination_staging_schema,
        destination_schema,
        destination_table,
        environment,
        time_delay,
        country,
        max_file_size: int=int(50e6),
    ):
        self.dag = dag,
        self.sql_directory = sql_directory,
        self.gcp_project_id = gcp_project_id,
        self.mysql_connection_id = mysql_connection_id,
        self.source_schema = source_schema,
        self.source_table = source_table,
        self.gcs_connection_id = gcs_connection_id,
        self.bq_connection_id = bq_connection_id,
        self.gcs_bucket = gcs_bucket,
        self.destination_staging_schema = destination_staging_schema,
        self.destination_schema = destination_schema,
        self.destination_table = destination_table,
        self.time_delay = time_delay,
        self.environment = environment,
        self.max_file_size = max_file_size,
        self.queries = self.get_pipeline_queries()
        self.schema_file = self.get_schema_files()
        self.country = country
    
    # variables
    data_lake_paths = GoogleCloudStoragePaths(self.destination_table) #<- the same Undefined Variable 'self' error is flagged here.

CodePudding user response：

since

    def __init__(self, ...):
        ...
    # this variable
    data_lake_paths = GoogleCloudStoragePaths(self.destination_table)

is outside of any class method that accepts a self parameter, python will set this as a class variable and not an instance variable, so no self parameter will be passed (that's why the Undefined Variable 'self' occurs).

Put that inside of the __init__ method or another method and it should work,.

CodePudding user response：

Variables defined straight into the body of a class cannot use self, only those in methods can. Instead, just move the definition of that variable into the __init__ function. If you need to have the variable even when __init__ has not been run, then just set it to None in the class body.

code:

class MySQLBatchPipeline:
    '''
    Class to generate MySQL batch pipelines that store CSV's
    in GCS then import them into BigQuery
    '''
    export_format='CSV'
    DESTINATION_TABLE_FORMAT = self.get_environment()   '.{dataset}.{table}'
    
    # Declare here if necessary
    data_lake_paths = None

    def __init__(
        self,
        dag,
        sql_directory,
        gcp_project_id,
        mysql_connection_id,
        source_schema,
        source_table,
        gcs_connection_id,
        bq_connection_id,
        gcs_bucket,
        destination_staging_schema,
        destination_schema,
        destination_table,
        environment,
        time_delay,
        country,
        max_file_size: int=int(50e6),
    ):
        self.dag = dag,
        self.sql_directory = sql_directory,
        self.gcp_project_id = gcp_project_id,
        self.mysql_connection_id = mysql_connection_id,
        self.source_schema = source_schema,
        self.source_table = source_table,
        self.gcs_connection_id = gcs_connection_id,
        self.bq_connection_id = bq_connection_id,
        self.gcs_bucket = gcs_bucket,
        self.destination_staging_schema = destination_staging_schema,
        self.destination_schema = destination_schema,
        self.destination_table = destination_table,
        self.time_delay = time_delay,
        self.environment = environment,
        self.max_file_size = max_file_size,
        self.queries = self.get_pipeline_queries()
        self.schema_file = self.get_schema_files()
        self.country = country

        # Define here
        data_lake_paths = GoogleCloudStoragePaths(self.destination_table)