return value of execute

Question

Is the return value of sqlite3.execute always self? i.e. can I safely return some_connection_obj.execute(...) or use method chaining? I fail to find relevant text in that document.

Answer 1

When documentation fails, look into the code (python 3.6.4):

At the _pysqlite_query_execute function end:

    if (PyErr_Occurred()) {
        self->rowcount = -1L;
        return NULL;
    } else {
        Py_INCREF(self);
        return (PyObject*)self;
    }
}

PyObject* pysqlite_cursor_execute(pysqlite_Cursor* self, PyObject* args)
{
    return _pysqlite_query_execute(self, 0, args);
}

So, unless an error occurred, the method returns self.

However, according to PEP 249 (for DB API 2) return values are not defined, which means you are on your own, and possibly the code you write in that way will not be portable among different DB API 2 implementations. And indeed, according to psycopg docs .execute returns None.

The answer is, one can't safely chain methods in a broader sense, because doing so limits future code reuse possibilities.