How to run python class method at command line

Question

I'm trying to connect to a sqllite database using:

class Sqllite_utilities(object):

    def __init__(self):

        parser = argparse.ArgumentParser()
        parser.add_argument("-s","--source", type=str,
                            help="source table from db")
        args = parser.parse_args()
        print(args)


        source_table= args.source

        db_path = "sqlite:///"+settings.SETTINGS_PATH+"\\data.db"

        dataset_db = dataset.connect(db_path)
        self.dataset_table = dataset_db[source_table]


    def missing_ids(self):

        for user in self.dataset_table:
            print(user['id'])


if __name__ == '__main__':
    Sqllite_utilities.missing_ids(sys.argv[1])

When I do:

$ python find_missing_records.py -s test

I get:

Traceback (most recent call last):
  File "find_missing_records.py", line 41, in <module>
    Sqllite_utilities.missing_ids(sys.argv[1])
TypeError: unbound method missing_ids() must be called with Sqllite_utilities instance as first argument (got str instance instead)
(contact2E)

What am I doing wrong?

Jean-François Fabre · Accepted Answer · 2017-03-14 20:23:02Z

4

When doing:

Sqllite_utilities.missing_ids(sys.argv[1])

you're calling the missing_ids instance method with sys.argv[1] (a string) as self (functional way to call instance methods, but with the wrong object), which explains the error message.

It's clear that you have to create an instance of your object before being able to use the instance methods (the ones without @staticmethod or @classmethod decorators):

if __name__ == '__main__':
    s = Sqllite_utilities()

the constructor parses the arguments, using argparse.ArgumentParser which uses sys.argv by default, so leave that aside, it'll work.

Then call your method on the instance:

s.missing_ids()

s is implicitly passed as self when calling missing_ids

answered Mar 14, 2017 at 20:23

Jean-François Fabre♦

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3 Comments

user1592380 Over a year ago

Thank you that works. With regard to "It's clear that you have to create an instance of your object before being able to use the instance methods (the ones without staticmethod or classmethod decorators)", are you saying that class and static methods do not need the class to be instantiated first, but other methods do?

Jean-François Fabre Over a year ago

yes, you can use class/static methods without any instance.

user1592380 Over a year ago

Thank you, that helps my understanding.

Community · Accepted Answer · 2017-05-23 10:29:56Z

1

As suggested from the top answer to this question: unbound method f() must be called with fibo_ instance as first argument (got classobj instance instead)

Add to your code:

if __name__ == '__main__':
    obj = Sqllite_utilities()
    s.missing_ids()

edited May 23, 2017 at 10:29

CommunityBot

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answered Mar 14, 2017 at 20:25

John Moutafis

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2 Comments

user1592380 Over a year ago

Thank you for the reference

John Moutafis Over a year ago

Happy to help mate :)

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