Source code for _dbi_sqlite

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
:Purpose:   This module contains the library's *SQLite* database methods
            and attribute accessors; which are a specialised version of
            the :class:`_dbi_base._DBIBase` class methods.

:Platform:  Linux/Windows | Python 3.10+
:Developer: J Berendt
:Email:     support@s3dev.uk

:Comments:  n/a

:Example:

    For class-specific usage examples, please refer to the docstring
    for the following classes:

        - :class:`_DBISQLite`

"""
# Silence the spurious IDE-based error.
# pylint: disable=import-error

from utils4 import utils
from utils4.user_interface import ui
# locals
from _dbi_base import _DBIBase


[docs] class _DBISQLite(_DBIBase): """This *private* class holds the methods and properties which are used for accessing SQLite databases. Note: This class is *not* designed to be interacted with directly. Rather, please use the :class:`database.DBInterface` class instead, as the proper interface class has an automatic switch for database interfaces, based on the ``sqlalchemy.Engine`` object which is created from the connection string. Args: connstr (str): The database-specific SQLAlchemy connection string. :Example Use: This low-level generalised class is designed to be inherited by the calling/wrapping class as:: >>> from dblib.database import DBInterface class MyDB(DBInterface): def __init__(self, connstr: str): super().__init__(connstr=('sqlite:////path/to/database.db')) """
[docs] def __init__(self, connstr: str): """SQLite database interface initialiser.""" super().__init__(connstr=connstr) self._verify_db_exists()
[docs] def table_exists(self, table_name: str, verbose: bool=False) -> bool: """Using the ``engine`` object, test if the given table exists. Args: table_name (str): Name of the table to test. verbose (bool, optional): Print a message if the table does not exist. Defaults to False. Returns: bool: True if the given table exists, otherwise False. """ params = {'table_name': table_name} stmt = ('select count(*) from sqlite_master ' 'where type = \'table\' ' 'and name = :table_name') exists = bool(self.execute_query(stmt, params=params, raw=True)[0][0]) if (not exists) & verbose: msg = f'Table does not exist: {self._engine.url.database}.{table_name}' ui.print_warning(text=msg) return exists
[docs] def _verify_db_exists(self): """Verify the database file exists. Raises: FileNotFoundError: Raised if the database file passed via the connection string does not exist. """ utils.fileexists(filepath=self.engine.url.database, error='raise')