_dbi_sqlite - Private database interface for SQLite
- Purpose:
This module contains the library's SQLite database methods and attribute accessors; which are a specialised version of the
_dbi_base._DBIBase
class methods.- Platform:
Linux/Windows | Python 3.10+
- Developer:
J Berendt
- Email:
- Comments:
n/a
- Example:
For class-specific usage examples, please refer to the docstring for the following classes:
- class _dbi_sqlite._DBISQLite(connstr: str)[source]
Bases:
_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
database.DBInterface
class instead, as the proper interface class has an automatic switch for database interfaces, based on thesqlalchemy.Engine
object which is created from the connection string.- Parameters:
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'))
- _PREFIX = '\n[DatabaseError]:'
- __annotations__ = {}
- _create_engine() sqlalchemy.engine.base.Engine
Create a database engine using the provided environment.
- Returns:
A sqlalchemy database engine object.
- Return type:
sqlalchemy.engine.base.Engine
- static _is_dangerous(stmt: str) bool
Perform a dirty security check for injection attempts.
- Parameters:
stmt (str) -- SQL statement to be potentially executed.
- Raises:
SecurityWarning -- If there are multiple semi-colons (
;
) in the statement, or any comment delimiters (--
).- Returns:
False if the checks pass.
- Return type:
bool
- _report_sa_error(msg: str, error: sqlalchemy.exc.SQLAlchemyError)
Report SQLAlchemy error to the terminal.
- Parameters:
msg (str) -- Additional error to be displayed. This message will be automatically prefixed with '[DatabaseError]: '
error (sqlalchemy.exc.SQLAlchemyError) -- Caught error object from the try/except block.
- static _result_to_df__cursor(result: sqlalchemy.engine.cursor.CursorResult) DataFrame
Convert a
CursorResult
object to a DataFrame.If the cursor did not return results, an empty DataFrame containing the column names only, is returned.
- Parameters:
result (sqlalchemy.engine.cursor.CursorResult) -- Object to be converted.
- Returns:
A
pandas.DataFrame
object containing the cursor's data.- Return type:
pd.DataFrame
- static _result_to_df__stored(result: object) DataFrame
Convert a
MySQLCursor.stored_results
object to a DataFrame.- Parameters:
result (object) -- The
cursor.stored_results()
object fromcall. (a sqlalchemy or mysql.connector procedure)
- Returns:
A DataFrame containing the results from the procedure call.
- Return type:
pd.DataFrame
- _verify_db_exists()[source]
Verify the database file exists.
- Raises:
FileNotFoundError -- Raised if the database file passed via the
connection string does not exist. --
- property engine
Accessor to the
sqlalchemy.engine.base.Engine
object.
- execute_query(stmt: str, params: dict = None, raw: bool = True) list | DataFrame | None
Execute a query statement.
Important
The following are not allowed to be executed by this method:
Statements containing multiple semi-colons (
;
).Statements containing a comment delimiter (
--
).
If found, a
SecurityWarning
will be raised by the_is_dangerous()
method.- Parameters:
stmt (str) -- Statement to be executed. The parameter bindings are to be written in colon format.
params (dict, optional) -- Parameter key/value bindings as a dictionary, if applicable. Defaults to None.
raw (bool, optional) -- Return the data in 'raw' (tuple) format rather than as a formatted DataFrame. Defaults to True for efficiency.
If the query did not return results and the
raw
argument is False, an empty DataFrame containing the column names only, is returned.Note
In the SQL query, the bind parameters are specified by name, using the format
:bind_name
. Theparams
dictionary argument must contain the associated parameter name/value bindings.Warning
Generally, whatever statement is passed into this method will be executed, and may have destructive implications.
This method contains a
commit
call.
If a statement is passed into this method, and the user has the appropriate permissions - the change will be committed.
... HC SVNT DRACONES.
- Returns:
If the
raw
parameter is True, a list of tuples containing values is returned. Otherwise, apandas.DataFrame
object containing the returned data is returned.If this method is called with a script which does not return results, for example a CREATE script, None is returned; regardless of the value passed to the
raw
parameter.- Return type:
list | pd.DataFrame | None
- table_exists(table_name: str, verbose: bool = False) bool [source]
Using the
engine
object, test if the given table exists.- Parameters:
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:
True if the given table exists, otherwise False.
- Return type:
bool