Use read-only SQLite connection (#165)

* Use read-only SQLite connection

* suggestion from ruff

* Update db.py

* Update db.py

* Update db.py

* fix interface

* ruff format

mendeleev/db.py

@@ -13,15 +13,21 @@ def get_package_dbpath() -> str:
     return os.path.join(os.path.abspath(os.path.dirname(__file__)), DBNAME)
 
 
-def get_engine(dbpath: str = None) -> Engine:
+def get_engine(dbpath: str = None, read_only: bool = True) -> Engine:
     """Return the db engine"""
     if not dbpath:
         dbpath = get_package_dbpath()
-    return create_engine("sqlite:///{path:s}".format(path=dbpath), echo=False)
+    if read_only:
+        connectstr = "sqlite:///file:{path:s}?mode=ro&nolock=1&uri=true".format(
+            path=dbpath
+        )
+    else:
+        connectstr = "sqlite:///{path:s}".format(path=dbpath)
+    return create_engine(connectstr, echo=False)
 
 
-def get_session(dbpath: str = None) -> Session:
+def get_session(dbpath: str = None, read_only: bool = True) -> Session:
     """Return the database session connection."""
-    engine = get_engine(dbpath=dbpath)
+    engine = get_engine(dbpath=dbpath, read_only=read_only)
     db_session = sessionmaker(bind=engine, autoflush=False, autocommit=False)
     return db_session()