Detect whether to fetch from psycopg2 cursor or not?

Question

Let's say if I execute the following command.

insert into hello (username) values ('me')

and I ran like

cursor.fetchall()

I get the following error

psycopg2.ProgrammingError: no results to fetch

How can I detect whether to call fetchall() or not without checking the query is "insert" or "select"?

Thanks.

Answer 1

Look at this attribute:

cur.description

After you have executed your query, it will be set to None if no rows were returned, or will contain data otherwise - for example:

(Column(name='id', type_code=20, display_size=None, internal_size=8, precision=None, scale=None, null_ok=None),)

Catching exceptions is not ideal because there may be a case where you're overriding a genuine exception.

Answer 2

Check whether cursor.pgresult_ptr is None or not.

cursor.execute(sql)
if cursor.pgresult_ptr is not None:
    cursor.fetchall()

Answer 3

The accepted answer using cur.description does not solve the problem any more. cur.statusmessage can be a solution. This returns SELECT 0 or INSERT 0 1. A simple string operation can then help determine the last query.