105 lines
3.5 KiB
Python
105 lines
3.5 KiB
Python
"""This module contains functionality for interacting with a PostgreSQL database. It will automatically handle error
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conditions (i.e. missing columns) without terminating the entire program. Use the :py:class:`DBConnector` class to
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handle database interactions, either as a standalone object or in a context manager."""
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from __future__ import annotations
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import os
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import psycopg2
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from psycopg2 import DatabaseError, OperationalError
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from psycopg2.errors import UndefinedColumn
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DB_ADDRESS = os.getenv('DB_ADDRESS', 'localhost')
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DB_PORT = os.getenv('DB_PORT', 5432)
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DB_USER = os.getenv('DB_USER', 'postgres')
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DB_PASSWORD = os.getenv('DB_PASSWORD', '')
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DB_NAME = os.getenv('DB_NAME', 'postgres')
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DB_TABLE = os.getenv('DB_TABLE', 'cables')
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class DBConnector:
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"""Context managed database class. Use with statements to automatically open and close the database connection, like
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so:
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.. code-block:: python
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with DBConnector() as db:
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db.read()
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"""
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def _db_start(self):
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"""Setup the database connection and cursor."""
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try:
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self.conn = psycopg2.connect(
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f"host={DB_ADDRESS} port={DB_PORT} dbname={DB_NAME} user={DB_USER} password={DB_PASSWORD}")
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self.cur = self.conn.cursor()
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except OperationalError as e:
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raise e
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def _db_stop(self):
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"""Close the cursor and connection."""
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self.cur.close()
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self.conn.close()
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def __init__(self):
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self._db_start()
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def __del__(self):
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self._db_stop()
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def __enter__(self):
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self._db_start()
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def __exit__(self):
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self._db_stop()
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def _query(self, sql) -> list[dict]:
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"""Basic function for running queries.
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:param sql: SQL query as plaintext.
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:return: Results of the query, or an empty list if none."""
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result = []
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try:
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self.cur.execute(sql)
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result = self._read_dict()
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except DatabaseError as e:
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print(f"ERROR {e.pgcode}: {e.pgerror}\n"
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f"Caused by query: {sql}")
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finally:
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return result
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def read(self, **kwargs) -> list[dict]:
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"""Read rows from a database that match the specified filters.
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:param kwargs: Column constraints; i.e. what value to filter by in what column.
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:returns: A list of dictionaries of all matching rows, or an empty list if no match."""
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args = []
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for kw in kwargs.keys():
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args.append(f"{kw} ILIKE {kwargs['kw']}")
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query = f"SELECT * FROM {DB_TABLE}"
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if len(args) > 0:
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query += f" WHERE {' AND '.join(args)}"
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return self._query(query)
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def write(self, **kwargs) -> dict:
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"""Write a row to the database.
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:param kwargs: Values to write for each database; specify each column separately!
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:returns: The row you just added."""
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values = []
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for val in kwargs.keys():
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values.append(kwargs[val])
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query = f"INSERT INTO {DB_TABLE} ({', '.join(kwargs.keys())}) VALUES ({', '.join(values)})"
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self._query(query)
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return kwargs
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def write_all(self, items: list[dict]) -> list[dict]:
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"""Write multiple rows to the database.
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:param items: Rows to write, as a list of dictionaries.
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:returns: The rows that were added successfully."""
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successes = []
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for i in items:
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res0 = self.write(**i)
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if res0:
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successes.append(res0)
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return successes
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