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POHow to improve the speed of a loop containing a sqlalchemy query statement as conditional
 

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    <p>This loop checks if a record is in the sqlite database and builds a list of dictionaries for those records that are missing and then executes a multiple insert statement with the list. This works but it is very slow (at least i think it is slow) as it takes 5 minutes to loop over 3500 queries. I am a complete newbie in python, sqlite and sqlalchemy so I wonder if there is a faster way of doing this.</p> <pre><code>list_dict = [] session = Session() for data in data_list: if session.query(Class_object).filter(Class_object.column_name_01 == data[2]).filter(Class_object.column_name_00 == an_id).count() == 0: list_dict.append({'column_name_00':a_id, 'column_name_01':data[2]}) conn = engine.connect() conn.execute(prices.insert(),list_dict) conn.close() session.close() </code></pre> <p>edit: I moved <code>session = Session()</code> outside the loop. Did not make a difference.</p> <p><strong>SOLUTION</strong>:</p> <p>thanks to <strong>mcabral</strong> answer I modified the code as:</p> <pre><code>existing_record_list = [] list_dict = [] conn = engine.connect() s = select([prices.c.column_name_01], prices.c.column_name_00==a_id) result = conn.execute(s) for row in result: existing_record_list.append(row[0]) for data in raw_data['data']: if data[2] not in existing_record_list: list_dict.append({'column_name_00':a_id, 'column_name_01':data[2]} conn = engine.connect() conn.execute(prices.insert(),list_dict) conn.close() </code></pre> <p>This now takes 6 seconds. That is some improvement!!</p>
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