add simple context manager for SqliteContainer, test passing

this allows automatic .close() to be called on connection objects.

sew/_core.py

@@ -33,6 +33,19 @@ def __init__(self, dbpath: str, row_factory: type=sq.Row, pragma_foreign_keys: b
 
         if pragma_foreign_keys:
             self.cur.execute("PRAGMA foreign_keys=ON")
+
+    def __enter__(self):
+        '''
+        For use in a with statement.
+        '''
+        return self
+
+    def __exit__(self, type, value, traceback):
+        '''
+        For use in a with statement.
+        Closes the connection for you, unlike default sqlite3.Connection.
+        '''
+        self.con.close()
 
 #%% Mixin to redirect common sqlite methods for brevity in code later
 class CommonRedirectMixin:

tests/correctness.py

@@ -634,6 +634,23 @@ def test_column_proxy_container(self):
         self.assertIs(container.col2, table.columns['col2'])
         self.assertIs(container.col3, table.columns['col3'])
 
+    def test_context_manager(self):
+        # Show that default sqlite3 doesn't close the database
+        with sq.connect(":memory:") as sqdb:
+            sqcur = sqdb.cursor()
+        sqcur.execute("create table x(c1 INT)")
+
+        # Then show that sew database does throw
+        with sew.Database(":memory:") as db:
+            cur = db.con.cursor()
+        # Extracting a cursor manually
+        with self.assertRaises(sq.ProgrammingError):
+            cur.execute('create table x(c1 INT)')
+        # Using our in-built executors
+        with self.assertRaises(sq.ProgrammingError):
+            db.execute('create table x(c1 INT)')
+
+
 
     #%% ==================================== PLUGINS ==================================== #
     def test_numpy_plugin(self):