Placing 2D Array from PostgreSQL Database into 2d List Python using Django Interface

Question

I'm attempting to retrieve information from a postgreSQL database, a single column to be specific within which the data is stored in a 2D array format

example :

('user1', 'user2,'user3'),('user1', 'user2,'user3'),('user1', 'user2,'user3')

I'm extracting the values into a values_list using django's database abstraction interface

q = DBReports.objects.all().filter(name__contains = name1)  
q = (q.values_list(columnName))

This then places all the values into a values_list, from this I need to extract two of the values from each list within the list, e.g user1 and user3 which are at array positions x,0,x,2 respectively, I am unable to determine how many lists within lists there will be, therefore I must iterate through the length

However I cannot convert the values_list to a 2D list, the following does not allow the code to be iteratable

list((q.values_list(columnName)))

And just returns a length of one, and all values in a single list.

Is there a way i can adequately extract this 2D list and place it into a 2D list within python?

Printed values are below (ignore all the '' its used later in the program)

[("[('user1', 'user2', 'user3', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user4', 'user5', 'user6', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user1', 'user3', 'user6', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user1', 'user2', 'user7', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user1', 'user2', 'user2', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '')]",)]

print q.values_list(columnName) for details.

Rajesh Kaushik
– Rajesh Kaushik

2015-08-17 11:47:43 +00:00
Commented Aug 17, 2015 at 11:47 — Rajesh Kaushik
– Rajesh Kaushik, Commented Aug 17, 2015 at 11:47
@RajeshKaushik Thanks, See above

kxdan
– kxdan

2015-08-17 11:54:41 +00:00
Commented Aug 17, 2015 at 11:54 — kxdan
– kxdan, Commented Aug 17, 2015 at 11:54

Rajesh Kaushik · Accepted Answer · 2015-08-17 12:17:23Z

1

You can get it done like this

import ast
q = DBReports.objects.all().filter(name__contains = name1)  
q = (q.values_list(columnName))
users_list = ast.literal_eval(q[0][0])

Check the users_list value

print users_list
[('user1', 'user2', 'user3', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user4', 'user5', 'user6', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user1', 'user3', 'user6', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user1', 'user2', 'user7', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', ''), ('user1', 'user2', 'user2', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '')]

This will enable iteration on users_list.

Note that ast.eval is safe to use. For more details read the docs here.

answered Aug 17, 2015 at 12:17

Rajesh Kaushik

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