Problem when recording data

Question

I’m performing a query on a table where the structure is :

Documento  Produto
123        Camisa Posh rosa
127        Calça Handara 36
127        Meia Barby 
158        Calça Handara 38
129        Blusa Yoll M
129        Blusa Yoll azul P
129        Short preto 36

In Python I created a course for this query, because my intention and save the results in a string separated by ,, but in that way:

Camisa Posh rosa,
Calça Handara 36, Meia Barby ,
Calça Handara 38,
Blusa Yoll M, Blusa Yoll azul P, Short preto 36

In this case he would take the products that are on the same coupon and write on a single line, but my problem is that he is doubling the amount of registration for these documents:

Camisa Posh rosa,
Calça Handara 36, Meia Barby ,
Calça Handara 36, Meia Barby ,
Calça Handara 38,
Blusa Yoll M, Blusa Yoll azul P, Short preto 36   
Blusa Yoll M, Blusa Yoll azul P, Short preto 36 
Blusa Yoll M, Blusa Yoll azul P, Short preto 36 

I believe I have to create a FOR to check the coupons and not repeat the data, however I am not able to play this logic in the code. Follows the code

import os
os.chdir("C:\\oracle\\product\\10.2.0\\client")
import cx_Oracle
con = cx_Oracle.connect('venda/[email protected]:1521/local')

curVendas = con.cursor()
curVendaProd = con.cursor()
base = ''

curVendas.execute('select * from base_venda')
for vendas in curVendas:
    print(vendas)

    quantidade = curVendaProd.execute('select produto from base_venda where documento = ' + str(vendas[0]))
    i = 1
    for produtos in curVendaProd:
        print(produtos)

        if (i == quantidade) :
            base = base + produtos[0]
        else:
            base = base + produtos[0] + ',' 
            i += 1

    base = base + '\n'

arquivo = open("base_import.csv", "w")
arquivo.write(base)
arquivo.close()