Python: PSQL: Generate list from query

Question

I am trying to retrieve some data from a table and output it as a list. The problem is that the resulting list is not in the correct form.

This is my table: enter image description here

My code:

cur.execute("SELECT tegebruikentags FROM tagstegebruiken WHERE wel_niet_lezen = True")
taglist = cur.fetchall()
print (taglist)

The output:

[('Bakkerij.Device1.DB100INT0',), ('Bakkerij.Device1.DB100INT4',), ('Bakkerij.Device1.DB100INT8',)]

The desired output:

['Bakkerij.Device1.DB100INT0', 'Bakkerij.Device1.DB100INT4', 'Bakkerij.Device1.DB100INT8']

How should I edit the code in order to get the list as I want?

Thanks in advance!

At the database side there are also the group aggregation functions: string_agg() , json_agg() etc — joop, Jul 17 '15 at 11:57

score 2 · Accepted Answer · answered Jul 17 '15 at 11:45

2

I'm not sure if you can do this automatically with the query, but this is a solution.

li = [item[0] for item in cur.fetchall()]
print li
'['Bakkerij.Device1.DB100INT0', 'Bakkerij.Device1.DB100INT4', 'Bakkerij.Device1.DB100INT8']'

answered Jul 17 '15 at 11:45

omri_saadon

score 0 · Answer 2 · answered Jul 17 '15 at 11:47

0

If you are using psycopg2 , cursor.fetchall returns a list of tuples, even if there is only a single column in it.

You can convert that list of tuples to a list using -

taglist = [i for item in taglist for i in item]

answered Jul 17 '15 at 11:47

Anand S Kumar

2 Answers2