init

core/conn.py

@@ -0,0 +1,37 @@
+from typing import Any, Iterator
+from contextlib import contextmanager
+import sqlalchemy as sa
+from sqlalchemy.orm import sessionmaker
+
+class Conn:
+	__slots__ = ('engine', 'session_factory', '_session', '_depth')
+	
+	engine: Any
+	session_factory: Any
+	_session: Any
+	_depth: int
+	
+	def __init__(self, conn_str: str) -> None:
+		self.engine = sa.create_engine(conn_str)
+		self.session_factory = sessionmaker(bind = self.engine)
+		self._session = None
+		self._depth = 0
+	
+	@contextmanager
+	def session(self) -> Iterator[Any]:
+		if self._depth > 0:
+			yield self._session
+			return
+		sess = self.session_factory()
+		self._session = sess
+		self._depth += 1
+		try:
+			yield sess
+			sess.commit()
+		except:
+			sess.rollback()
+			raise
+		finally:
+			sess.close()
+			self._session = None
+			self._depth -= 1