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

View File

@ -275,28 +275,50 @@ alias::
cursor = connections['my_db_alias'].cursor()
# Your code here...
By default, the Python DB API will return results without their field
names, which means you end up with a ``list`` of values, rather than a
``dict``. At a small performance cost, you can return results as a
``dict`` by using something like this::
By default, the Python DB API will return results without their field names,
which means you end up with a ``list`` of values, rather than a ``dict``. At a
small performance and memory cost, you can return results as a ``dict`` by
using something like this::
def dictfetchall(cursor):
"Returns all rows from a cursor as a dict"
"Return all rows from a cursor as a dict"
desc = cursor.description
return [
dict(zip([col[0] for col in desc], row))
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.fetchall()
((54360982L, None), (54360880L, None))
((54360982, None), (54360880, None))
>>> cursor.execute("SELECT id, parent_id FROM test LIMIT 2");
>>> 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
-----------------------