Work on native gui: views and database model

yms/database.py

@@ -20,6 +20,7 @@ class Database():
         except MySQLdb.Error as e:
             self.error = e
             return False
+        self.conn.autocommit(False)
         self.cur = self.conn.cursor()
         self.dcur = self.conn.cursor(MySQLdb.cursors.DictCursor)
         return True
@@ -54,3 +55,29 @@ class Database():
         text = self.error.args[1]
         self.error = None
         return(code, text)
+
+    def execute_write(self, sql, values=(), expected_rows=None):
+        """
+        Execute an INSERT, UPDATE, or DELETE statement.
+        expected_rows:
+            None = do not check the number of affected rows
+            1    = expect exactly one affected row
+            0    = expect no affected rows
+        """
+        try:
+            self.cur.execute(sql, values)
+        except MySQLdb.Error as e:
+            self.rollback()
+            self.error = e
+            return False
+        if (expected_rows is not None and self.cur.rowcount != expected_rows):
+            self.rollback()
+            self.error = RuntimeError(
+                "Expected {} affected rows, got {}".format(
+                    expected_rows,
+                    self.cur.rowcount
+                )
+            )
+            return False
+        self.error = None
+        return True