Fixed #25326 -- Added namedtuple example for executing custom SQL.

This commit is contained in:
Dražen Odobašić 2015-08-29 16:54:51 +02:00 committed by Tim Graham
parent 40bf18e702
commit 5ab65ca5c9
1 changed files with 30 additions and 8 deletions

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@ -275,28 +275,50 @@ alias::
cursor = connections['my_db_alias'].cursor() cursor = connections['my_db_alias'].cursor()
# Your code here... # Your code here...
By default, the Python DB API will return results without their field By default, the Python DB API will return results without their field names,
names, which means you end up with a ``list`` of values, rather than a which means you end up with a ``list`` of values, rather than a ``dict``. At a
``dict``. At a small performance cost, you can return results as a small performance and memory cost, you can return results as a ``dict`` by
``dict`` by using something like this:: using something like this::
def dictfetchall(cursor): def dictfetchall(cursor):
"Returns all rows from a cursor as a dict" "Return all rows from a cursor as a dict"
desc = cursor.description desc = cursor.description
return [ return [
dict(zip([col[0] for col in desc], row)) dict(zip([col[0] for col in desc], row))
for row in cursor.fetchall() for row in cursor.fetchall()
] ]
Here is an example of the difference between the two:: Another option is to use :func:`collections.namedtuple` from the Python
standard library. A ``namedtuple`` is a tuple-like object that has fields
accessible by attribute lookup; it's also indexable and iterable. Results are
immutable and accessible by field names or indices, which might be useful::
from collections import namedtuple
def namedtuplefetchall(cursor):
"Return all rows from a cursor as a namedtuple"
desc = cursor.description
nt_result = namedtuple('Result', [col[0] for col in desc])
return [nt_result(*row) for row in cursor.fetchall()]
Here is an example of the difference between the three::
>>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2"); >>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2");
>>> cursor.fetchall() >>> cursor.fetchall()
((54360982L, None), (54360880L, None)) ((54360982, None), (54360880, None))
>>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2"); >>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2");
>>> dictfetchall(cursor) >>> dictfetchall(cursor)
[{'parent_id': None, 'id': 54360982L}, {'parent_id': None, 'id': 54360880L}] [{'parent_id': None, 'id': 54360982}, {'parent_id': None, 'id': 54360880}]
>>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2");
>>> results = namedtuplefetchall(cursor)
>>> results
[Result(id=54360982, parent_id=None), Result(id=54360880, parent_id=None)]
>>> results[0].id
54360982
>>> results[0][0]
54360982
Connections and cursors Connections and cursors
----------------------- -----------------------