locopy.database module

Database Module

class locopy.database.Database(dbapi, config_yaml=None, **kwargs)

Bases: object

This is the base class for all DBAPI 2 database connectors which will inherit this functionality. The Database class will manage connections and handle executing queries. Most of the functionality should work out of the box for classes which inherit minus the abstract method for connect which may vary across databases.

Parameters:

• dbapi (DBAPI 2 module, optional) – A database adapter which is Python DB API 2.0 compliant (psycopg2, pg8000, etc.)

• config_yaml (str, optional) – String representing the YAML file location of the database connection keyword arguments. It is worth noting that this should only contain valid arguments for the database connector you plan on using. It will throw an exception if something is passed through which isn’t valid.

• **kwargs – Database connection keyword arguments.

dbapi

database adapter which is Python DBAPI 2.0 compliant

Type:

DBAPI 2 module

connection

Dictionary of database connection items

Type:

dict

conn

DBAPI connection instance

Type:

dbapi.connection

cursor

DBAPI cursor instance

Type:

dbapi.cursor

Raises:

CredentialsError – Database credentials are not provided, valid, or both kwargs and a YAML config was provided.

column_names()

Pull column names out of the cursor description. Depending on the DBAPI, it could return column names as bytes: b'column_name'

Returns:

List of column names, all in lower-case

Return type:

list

connect()

Creates a connection to a database by setting the values of the conn and cursor attributes.

Raises:

DBError – If there is a problem establishing a connection.

disconnect()

Terminates the connection by closing the values of the conn and cursor attributes.

Raises:

DBError – If there is a problem disconnecting from the database.

execute(sql, commit=True, params=(), many=False, verbose=True)

Execute some sql against the connection.

Parameters:

• sql (str) – SQL to run against the connection. Could be one or multiple statements.

• commit (Boolean, default True) – Whether to “commit” the commands to the cluster immediately or not.

• params (iterable of parameters) – Parameters to submit with the query. The exact syntax will depend on the database adapter you are using

• many (bool, default False) – Whether to execute the script as an “execute many”

• verbose (bool, default True) – Whether to print executed query

Raises:

• DBError – if a problem occurs executing the sql statement

• DBError – If a connection to the database cannot be made

to_dataframe(size=None)

Return a dataframe of the last query results. This imports Pandas in here, so that it’s not needed for other use cases. This is just a convenience method.

Parameters:

size (int, optional) – Chunk size to fetch. Defaults to None.

Returns:

Dataframe with lowercase column names. Returns None if no fetched result.

Return type:

pandas.DataFrame

to_dict()

Generate dictionaries of rows

Yields:

dict – Each row, encoded as a dict.