Coverage for /var/devmt/py/dbilib_0.0.1.dev1/dbilib/_dbi_sqlite.py: 100%

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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 

28from _dbi_base import _DBIBase 

29 

30 

31class _DBISQLite(_DBIBase): 

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

33 used for accessing SQLite databases. 

34 

35 Note: 

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

37 

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

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

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

41 object which is created from the connection string. 

42 

43 Args: 

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

45 string. 

46 

47 :Example Use: 

48 

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

50 the calling/wrapping class as:: 

51 

52 >>> from dblib.database import DBInterface 

53 

54 class MyDB(DBInterface): 

55 

56 def __init__(self, connstr: str): 

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

58 

59 """ 

60 

61 def __init__(self, connstr: str): 

62 """SQLite database interface initialiser.""" 

63 super().__init__(connstr=connstr) 

64 self._verify_db_exists() 

65 

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

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

68 

69 Args: 

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

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

72 not exist. Defaults to False. 

73 

74 Returns: 

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

76 

77 """ 

78 params = {'table_name': table_name} 

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

80 'where type = \'table\' ' 

81 'and name = :table_name') 

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

83 if (not exists) & verbose: 

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

85 ui.print_warning(text=msg) 

86 return exists 

87 

88 def _verify_db_exists(self): 

89 """Verify the database file exists. 

90 

91 Raises: 

92 FileNotFoundError: Raised if the database file passed via the 

93 connection string does not exist. 

94 

95 """ 

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