read_data

pyhelpers.dbms.utils.read_data(db_instance, schema_name, table_name, sql_query=None, data_name='data', prefix='', suffix='', verbose=False, **kwargs)[source]

Load data from the project database.

Parameters:

  • db_instance (Any) – a class instance for handling a database

  • schema_name (str) – name of a schema

  • table_name (str) – name of a table

  • sql_query (str | None) – SQL statement for querying data, defaults to None

  • data_name (str) – name of the data, defaults to "data"

  • prefix (str) – prefix for data_name, defaults to ''

  • suffix (str) – suffix for data_name, defaults to ''

  • verbose (bool | int) – whether to print relevant information in console, defaults to False

  • kwargs – [optional] parameters of the method pyhelpers.dbms.PostgreSQL.read_sql_query or pyhelpers.dbms.MSSQL.read_table

Returns:

queried data

Return type:

pandas.DataFrame | None

Examples:

>>> from pyhelpers.dbms.utils import import_data, read_data
>>> from pyhelpers.dbms import PostgreSQL
>>> from pyhelpers._cache import example_dataframe

>>> testdb_name = 'testdb'
>>> testdb = PostgreSQL('localhost', 5432, 'postgres', database_name=testdb_name)
Password (postgres@localhost:5432): ***
Creating a database: "testdb" ... Done.
Connecting postgres:***@localhost:5432/testdb ... Successfully.

>>> # Import an example dataframe into a table named "points"."England"
>>> example_df = example_dataframe()
>>> test_schema_name = 'points'
>>> test_table_name = 'England'
>>> test_data_name = 'the data of "England points"'
>>> import_data(
...     testdb, example_df, test_schema_name, test_table_name, test_data_name, index=True,
...     verbose=True)
To import the data of "England points" into "points"."England"?
 [No]|Yes: yes
Importing the data ... Done.

>>> # Retrieve the data
>>> example_df_ = read_data(
...     testdb, test_schema_name, test_table_name, data_name=test_data_name,
...     index_col='City', verbose=True)
Reading the data of "England points" from "points"."England" ... Done.

>>> # Check whether the retrieved data is the same as the original example dataframe
>>> example_df_.equals(example_df)
True

>>> # Delete the database "testdb"
>>> testdb.drop_database(verbose=True)
To drop the database "testdb" from postgres:***@localhost:5432
? [No]|Yes: yes
Dropping "testdb" ... Done.