cursor.description returns non-pep249 complaint value '()'

[zzzeek]

Per pep 249, cursor.description is to be a sequence of 7-item tuples describing the columns in a result set. If the operation does not return rows, it is required to be None:

This attribute will be None for operations that do not return rows or if the cursor has not had an operation invoked via the .execute*() method yet.

Per the test case below, a simple "DELETE" SQL statement is returning an empty tuple, rather than None:

from pysqlite2 import dbapi2

print dbapi2.version_info

conn = dbapi2.connect(":memory:")
cursor = conn.cursor()

cursor.execute("""
    CREATE TABLE plain_pk (
    id INTEGER NOT NULL,
    data VARCHAR(50),
    PRIMARY KEY (id)
)
""")

cursor.executemany("""
    INSERT INTO plain_pk (id, data) VALUES (?, ?)
""", ((1, 'd1'), (2, 'd2'), (3, 'd3')))

cursor.execute("""
    DELETE FROM plain_pk WHERE plain_pk.id = ?
""", (2,))

assert cursor.description is None, cursor.description

output:

(2, 8, 2)
Traceback (most recent call last):
  File "test.py", line 24, in <module>
    assert cursor.description is None, cursor.description
AssertionError: ()

this is a behavioral regression which breaks downstream projects such as SQLAlchemy.

[ghaering]

Thanks for reporting this. As I see SQLAlchemy as critical, and the only sensible way to work with databases in Python ;-) - I just released version 2.8.3 with the fix.

[zzzeek]

thanks a ton for fixing this so quick!!