Coverage for /var/devmt/py/dbilib_0.5.0/dbilib/_dbi_sqlite.py: 100%

1#!/usr/bin/env python3 

2# -*- coding: utf-8 -*- 

3""" 

4:Purpose: This module contains the library's *SQLite* database methods 

5 and attribute accessors; which are a specialised version of 

6 the :class:`_dbi_base._DBIBase` class methods. 

7 

8:Platform: Linux/Windows | Python 3.10+ 

9:Developer: J Berendt 

10:Email: support@s3dev.uk 

11 

12:Comments: n/a 

13 

14:Example: 

15 

16 For class-specific usage examples, please refer to the docstring 

17 for the following classes: 

18 

19 - :class:`_DBISQLite` 

20 

21""" 

22# Silence the spurious IDE-based error. 

23# pylint: disable=import-error 

24 

25from utils4 import utils 

26from utils4.user_interface import ui 

27# locals 

28try: 

29 from ._dbi_base import _DBIBase 

30except ImportError: 

31 from _dbi_base import _DBIBase 

32 

33 

34class _DBISQLite(_DBIBase): 

35 """This *private* class holds the methods and properties which are 

36 used for accessing SQLite databases. 

37 

38 Note: 

39 This class is *not* designed to be interacted with directly. 

40 

41 Rather, please use the :class:`database.DBInterface` class 

42 instead, as the proper interface class has an automatic switch 

43 for database interfaces, based on the ``sqlalchemy.Engine`` 

44 object which is created from the connection string. 

45 

46 Args: 

47 connstr (str): The database-specific SQLAlchemy connection 

48 string. 

49 

50 :Example Use: 

51 

52 This low-level generalised class is designed to be inherited by 

53 the calling/wrapping class as:: 

54 

55 >>> from dbilib.database import DBInterface 

56 

57 class MyDB(DBInterface): 

58 

59 def __init__(self, connstr: str): 

60 super().__init__(connstr=('sqlite:////path/to/database.db')) 

61 

62 """ 

63 

64 def __init__(self, connstr: str): 

65 """SQLite database interface initialiser.""" 

66 super().__init__(connstr=connstr) 

67 self._verify_db_exists() 

68 

69 def table_exists(self, table_name: str, verbose: bool=False) -> bool: 

70 """Using the ``engine`` object, test if the given table exists. 

71 

72 Args: 

73 table_name (str): Name of the table to test. 

74 verbose (bool, optional): Print a message if the table does 

75 not exist. Defaults to False. 

76 

77 Returns: 

78 bool: True if the given table exists, otherwise False. 

79 

80 """ 

81 params = {'table_name': table_name} 

82 stmt = ('select count(*) from sqlite_master ' 

83 'where type = \'table\' ' 

84 'and name = :table_name') 

85 exists = bool(self.execute_query(stmt, params=params, raw=True)[0][0]) 

86 if (not exists) & verbose: 

87 msg = f'Table does not exist: {self._engine.url.database}.{table_name}' 

88 ui.print_warning(text=msg) 

89 return exists 

90 

91 def _verify_db_exists(self): 

92 """Verify the database file exists. 

93 

94 Raises: 

95 FileNotFoundError: Raised if the database file passed via the 

96 connection string does not exist. 

97 

98 """ 

99 utils.fileexists(filepath=self.engine.url.database, error='raise')