`comdb2.factories` Factory functions for use with Comdb2 handles

This module provides factory functions for use with Comdb2 handles.

Both dbapi2.Connection and cdb2.Handle have a public row_factory property that can be used to control the type used for result rows. By default, each row is returned as a list, but you can receive the row as a collections.namedtuple by using namedtuple_row_factory as the row_factory. Likewise you can receive the row as a dict by using dict_row_factory.

A factory function will be called with a list of column names, and must return a callable that will be called once per row with a list of column values.

comdb2.factories.dict_row_factory(col_names)[source]

Return each result row as a dict mapping column names to values.

Note

You will not be able to use this factory if your result set includes duplicated column names. This can happen when joining across tables that use the same name for a foreign key column, for instance. To avoid duplicating column names, avoid using SELECT * with joins.

You may also be able to use the USING clause on the join to avoid duplicating column names. This query would duplicate the id column:

SELECT * FROM a INNER JOIN b ON a.id = b.id

Whereas this one wouldn’t:

SELECT * FROM a INNER JOIN b USING(id)

Example

>>> conn.row_factory = dict_row_factory
>>> row = conn.cursor().execute("select 1 as x, 2 as y").fetchone()
>>> print(row)
{'y': 2, 'x': 1}
>>> print(row['x'])
1

comdb2.factories.namedtuple_row_factory(col_names)[source]

Return each result row as a collections.namedtuple.

The fields of the namedtuple are set to the names of the result set columns, in positional order.

Note

You will not be able to use this factory if your result set includes columns whose names aren’t valid Python attribute names. Make sure to assign each column a name starting with a letter and containing only alphanumeric characters and underscores. Also make sure that column names aren’t Python reserved words. You can control column names by using AS in your SQL query, as in:

SELECT count(*) AS rowcount

Note

You will not be able to use this factory if your result set includes duplicated column names. This can happen when joining across tables that use the same name for a foreign key column, for instance. To avoid duplicating column names, avoid using SELECT * with joins.

You may also be able to use the USING clause on the join to avoid duplicating column names. This query would duplicate the id column:

SELECT * FROM a INNER JOIN b ON a.id = b.id

Whereas this one wouldn’t:

SELECT * FROM a INNER JOIN b USING(id)

Example

>>> conn.row_factory = namedtuple_row_factory
>>> row = conn.cursor().execute("select 1 as x, 2 as y").fetchone()
>>> print(row)
Row(x=1, y=2)
>>> print(row.x)
1

comdb2.factories Factory functions for use with Comdb2 handles

`comdb2.factories` Factory functions for use with Comdb2 handles