Trying to work with data from a query using Python.

[Peter Otten]

ethereal_robe at hotmail.com wrote:

> Hello, I'm working with PostgreSQL and Python to obtain 2 columns froma 
> database and need to print it in a specific format.
> 
> Here is my current code.
> 
> 
> 
> #!/usr/bin/python
> # -*- coding: utf-8 -*-
> 
> import psycopg2
> import sys
> 
> con = None
> 
> try:
>      
>     con = psycopg2.connect(database='DB', user='ME', password='1234')
>     
>     cur = con.cursor()
>     cur.execute(" select Account_Invoice.amount_untaxed, right
>     (Res_Partner.vat,length(Res_Partner.vat)-2) as RFC from
>     Account_Invoice inner join Res_Partner on Account_Invoice.partner_id =
>     Res_Partner.id inner join Account_Invoice_Tax on Account_Invoice.id =
>     Account_Invoice_Tax.invoice_id where account_invoice.journal_id=2 and
>     account_invoice.date_invoice >= '2013-01-01' and
>     account_invoice.date_invoice <= '2013-02-01' and
>     account_invoice.reconciled is TRUE and account_invoice_tax.account_id
>     = 3237 and account_invoice.amount_tax >= 0;")
> 
>     rows = cur.fetchall()
> 
>     for row in rows:
>         print row
>     
> 
> except psycopg2.DatabaseError, e:
>     print 'Error %s' % e
>     sys.exit(1)
>     
>     
> finally:
>     
>     if con:
>         con.close()
> 
> 
> 
> 
> Now assume that fetchall would print the following:
> 
> LOEL910624ND5 from the column vat as RFC.
> 227 from the column amount_untaxed.
> 
> 
> Now I would need to print that in the following format.
> 
> 04|85|LOEL910624ND5|||||227|||||||||||||||
> 
> 04 always goes in the first column and 85 always goes in the second, vat
> goes in the third and the amount_untaxed goes in the eight column but we
> still need to have 22 columns in total.

Keep it simple:

COLUMN_COUNT = 22
TEMPLATE = "04|85|{0}|||||{1}|||||||||||||||"
assert TEMPLATE.count("|") == COLUMN_COUNT -1, "You cannot count ;)"

for row in cur.fetchall():
    print TEMPLATE.format(*row)

A bit more general:

fill_rows(rows):
    out_row = [""] * 22
    out_row[0] = "04"
    out_row[1] = "85"

    for row in rows:
        out_row[2], out_row[7] = row
        # copying not necessary here, but let's play it safe
        yield out_row[:] 

writer = csv.writer(sys.stdout, delimiter="|")
writer.writerows(fill_rows(cur.fetchall()))

All untested code.