start implementing column parity

database.py

@@ -1,6 +1,8 @@
 """This module contains functionality for interacting with a PostgreSQL database. It will automatically handle error
 conditions (i.e. missing columns) without terminating the entire program. Use the :py:class:`DBConnector` class to
 handle database interactions, either as a standalone object or in a context manager."""
+from __future__ import annotations
+
 import os
 import psycopg2
 from psycopg2 import DatabaseError, OperationalError
@@ -22,7 +24,9 @@ class DBConnector:
        with DBConnector() as db:
            db.read()
     """
+
     def _db_start(self):
+        """Setup the database connection and cursor."""
         try:
             self.conn = psycopg2.connect(
                 f"host={DB_ADDRESS} port={DB_PORT} dbname={DB_NAME} user={DB_USER} password={DB_PASSWORD}")
@@ -31,6 +35,7 @@ class DBConnector:
             raise e
 
     def _db_stop(self):
+        """Close the cursor and connection."""
         self.cur.close()
         self.conn.close()
 
@@ -46,14 +51,50 @@ class DBConnector:
     def __exit__(self):
         self._db_stop()
 
+    def _get_cols(self) -> set[str]:
+        """Get the list of columns in the database.
+
+        :return: A list of column names."""
+        query = f"select COLUMN_NAME from information_schema.columns where table_name={DB_TABLE}"
+        rows = {x["COLUMN_NAME"] for x in self._query(query)}
+        return rows
+
+    def _column_parity(self, columns: list[str] | set[str]) -> set[str]:
+        """If the listed columns are not in the database, add them."""
+        cols = set(columns)
+        existing = self._get_cols()
+        needs = cols.difference(existing.intersection(cols))
+        query = f"ALTER TABLE {DB_TABLE} {', '.join([f'ADD COLUMN {c}' for c in needs])}"
+        self._query(query)
+        return self._get_cols()
+
     def _query(self, sql) -> list[dict]:
+        """Basic function for running queries.
+
+        :param sql: SQL query as plaintext.
+        :return: Results of the query, or an empty list if none."""
+        result = []
         try:
             self.cur.execute(sql)
-            result = self.cur.fetchall()
+            result = self._read_dict()
         except DatabaseError as e:
-            print(f"DB ERROR [{e.pgcode}]: {e.pgerror}")
-            result = []
-        return result
+            print(f"ERROR {e.pgcode}: {e.pgerror}\n"
+                  f"Caused by query: {sql}")
+        finally:
+            return result
+
+    def _read_dict(self) -> list[dict]:
+        """Read the cursor as a list of dictionaries. psycopg2 defaults to using a list of tuples, so we want to convert
+        each row into a dictionary before we return it."""
+        cols = [i.name for i in self.cur.description]
+        results = []
+        for row in self.cur:
+            row_dict = {}
+            for i in range(0, len(row)):
+                if row[i]:
+                    row_dict = {**row_dict, cols[i]: row[i]}
+            results.append(row_dict)
+        return results
 
     def read(self, **kwargs) -> list[dict]:
         """Read rows from a database that match the specified filters.
@@ -90,4 +131,4 @@ class DBConnector:
             res0 = self.write(**i)
             if res0:
                 successes.append(res0)
-        return successes
+        return successes