CODEWITHSUNDEEP
pythonsqlalchemy
Zu Jiry
Zu Jiry

Reputation: 295

Return then wait for another function to finish in python

My general idea is, that I have a or more test functions which can call another function. So:

  1. test_function does some things, then calls another function
  2. Called other function will do something, then return a result and
  3. Wait for the test_function to finish, then do everything that is to be done after the "return"

Of course, that does not work with a literal return, so my question is, if there is a possibility I do not see.

A practical example:

Test function in pytest - test_config is a fixture:

def test_load_into_database(test_config):
    logger.info('Testing load_into_database')
    data = {
        'filename': 'file_0'
    }
    accessor = list(database_accessor(test_config))[0]
    access_data = accessor['session'].query(accessor['table']).all()
    assert access_data[0].filename != data['filename']
    accessor['session'].add(accessor['table'](
        filename='file_0'
    ))
    accessor['session'].commit()
    access_data = accessor['session'].query(accessor['table']).all()
    assert access_data[0].filename == data['filename']

This test function calls another one:

def database_accessor(cfg):
    setup = 'mysql+pymysql://{}:{}@{}/{}'.format(
        cfg['database_user'],
        cfg['database_passwd'],
        cfg['database_host'],
        cfg['database_db']
    )
    Base = automap_base()
    engine = create_engine(setup, echo=False)
    Base.prepare(engine, reflect=True)
    table = Base.classes.get(cfg['database_table'])
    session = Session(engine)
    ->return and wait<- {
        'session': session,
        'table': table
    }
    session.close()
    with engine.connect() as con:
        con.execution_options(autocommit=True).execute("TRUNCATE TABLE {}".format(cfg['database_table']))

What I want is, that the database_accessor returns the dictionary, then waits for the underlying function (in this case the test_function) to finish, then resumes.

That way, it is possible to use a variable number of test functions with the same database_accessor without executing all the different test functions in the database_accessor.

Callbacks

I know that there is a way, with a callback function, but that doubles my functions, which I do not want. E.g.

def test_load_into_database():
    database_accessor(load_into_database_1, var1, var2)

def database_accessor(function, args*):
    # do stuff
    function(args, stuff)
    # do other stuff

def load_into_database_1(args, stuff):
    # do something

Upvotes: 0

Views: 297

Answers (1)

Jasmijn
Jasmijn

Reputation: 10452

I think you'd want to make database_accessor a context manager:

with database_accessor(test_config) as accessor:
    access_data = accessor['session'].query(accessor['table']).all()
    assert access_data[0].filename != data['filename']
    accessor['session'].add(accessor['table'](
        filename='file_0'
    ))
    accessor['session'].commit()
    access_data = accessor['session'].query(accessor['table']).all()
    assert access_data[0].filename == data['filename']

The implementation would looks something like this:

from contextlib import contextmanager

@contextmanager
def database_accessor(cfg):
    setup = 'mysql+pymysql://{}:{}@{}/{}'.format(
        cfg['database_user'],
        cfg['database_passwd'],
        cfg['database_host'],
        cfg['database_db']
    )
    Base = automap_base()
    engine = create_engine(setup, echo=False)
    Base.prepare(engine, reflect=True)
    table = Base.classes.get(cfg['database_table'])
    session = Session(engine)
    try:
        yield {
        'session': session,
        'table': table
        }
    finally:
        session.close()
        with engine.connect() as con:
            con.execution_options(autocommit=True).execute("TRUNCATE TABLE {}".format(cfg['database_table']))

In this case, I would modify it slightly to yield a tuple instead of a dict:

yield session, table

and then, when using it you could do:

with database_accessor(test_config) as (session, table):

Upvotes: 1

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