pyscopg2: Is it possible to dynamically add %s in loop

Question

I am trying to create a method in python insert records into a table passing in a list of column names, and an associated list of records.

I was able to set it up where

Answer 1

You can use sql.Placeholder, to populate the sql statement with the amount of %s-placeholders you need:

def load_table(dbname,table_name,fields,records):
        con, cur = create_connection('foo')
        query = sql.SQL("insert into {} ({}) values ({})").format(
            sql.Identifier(table_name),
            sql.SQL(', ').join(map(sql.Identifier, fields)),
            sql.SQL(', ').join(sql.Placeholder() * len(fields)))
        print(query.as_string(con))


if __name__ == '__main__':
    dbname = '...'
    table_name = 'messages'
    fields = ['user_id', 'message_type', 'message_title']
    records = [['12345', 'json', 'my first message'], ]

load_table(dbname,table_name,fields,records)

Output:

insert into "messages" ("user_id", "message_type", "message_title") values (%s, %s, %s)