Python Flask - Easy Querying Function

Question

Can somebody explain me the last line return (rv[0] if rv else None) if one else rv ? Especially the role of one.

def query_db(query, args=(), one=False):
    cur = g.db.execute(query, args)
    rv = [dict((cur.description[idx][0], value)
               for idx, value in enumerate(row)) for row in cur.fetchall()]
    return (rv[0] if rv else None) if one else rv

score 2 · Accepted Answer · answered Sep 21 '11 at 01:01

2

one indicates whether or not to return only a single record. If one is true then it returns the first (rv[0]) if there are records to be found (if rv), otherwise it returns all the records.

answered Sep 21 '11 at 01:01

Ignacio Vazquez-Abrams

776,304
153
1,341
1,358

Thank you very much to all of you. – Max Sep 21 '11 at 01:07
What about just returning rv? The returned value can be iterated then. It is not clear why used two conditions. Maybe neither were needed. – Alisa Feb 02 '15 at 20:05
@Alisa: Sure, but you'll have to ask whoever wrote the code. – Ignacio Vazquez-Abrams Feb 02 '15 at 20:17

score 1 · Answer 2 · answered Sep 21 '11 at 01:02

1

By default, one is False, so by default the list-of-dicts generated from the fetchall gets returned.

If you pass True for one, you get only the first row (turned into a dict) of the query, or None if the query didn't return any rows.

answered Sep 21 '11 at 01:02

agf

171,228
44
289
238

Python Flask - Easy Querying Function

2 Answers2