Consider using identity comparison with singleton PTC-W0068
Bug risk
Major
5 months ago
—
3 years old
Comparison to singleton
None should be expr is None516
517 stream = VideoStream.query.get(stream.id)
518
519 assert stream == None520
521
522def test_edit_stream_user_error(db, client, jwt):Comparison to singleton
None should be expr is None500
501 stream = VideoStream.query.get(stream.id)
502
503 assert stream == None504
505
506def test_delete_stream_event_organizer(db, client, user, jwt):Comparison to singleton
None should be expr is None215
216 stream = VideoStream.query.get(stream.id)
217
218 assert stream == None219
220
221def test_edit_stream_organizer(db, client, user, jwt):Comparison to singleton
None should be expr is None 57 attendee_id = attendee.id
58 delete_ticket_holders_no_order_id()
59 ticket_holder = TicketHolder.query.get(attendee_id)
60 assert ticket_holder == None 61
62
63def test_send_monthly_invoice(db):Comparison to singleton
None should be expr is not None 47 attendee_id = attendee.id
48 delete_ticket_holders_no_order_id()
49 ticket_holder = TicketHolder.query.get(attendee_id)
50 assert ticket_holder != None 51
52
53def test_delete_ticket_holders_with_no_order_id(db):
Description
Comparisons to the singleton objects, like True, False, and None, should be done with identity, not equality. Use is or is not.
Identity checks are faster than equality checks.
Also, the equality checks can result in unintended behaviour in some cases:
>>> 1 is True
False
>>> 1 == True
True
>>> 1.0 is True
False
>>> 1.0 == True
True
Bad practice
value = fx()
if value == True: # `==` can cause unintended behaviour
print(value)
if value != None:
print(value)
Recommended
value = fx()
if value is True: # `is` for Identity comparison
print(value)
if value is not None:
print(value)
Exceptions:
Equality comparisons might be required in some cases, especially in SQLAlchemy, SQLObject, ORMs, etc. In these cases, it is safe to ignore this issue.