Question

I am fetching data for too many users from DB , the array in which all data is collected having two rows for each user , only last column value is different rest of the values are same like

r1 --> a , b , c , d , 1 (user1)
r2 -- > a , b , c , d , 2 (user1)
r3 --> z , x , v , n , 3 (user2)
r4 -- > z , x , v , n , 4 (user2)

Now I want to create an array which include only one row corresponding to each user but consist of every value like

r1 --> a , b , c , d , 1 , 2 (user1)
r2 -- >z , x , v , n , 3 , 4 (user2)

I have tried for loop , but the resulted array consist of only last record , I wanted an array which consist of all the records for all users.

e.g.

cursor.execute("some query ")
    numrows = int(cursor.rowcount) 

let this num rows returns value 4.

then

for I in range(numrows):

pass

will loop 4 times , but actually it consist the values for two users.

but when I returns the resulted array it consist the value of last user only.

So please suggest me some way so that when I do this for I in range(numrows): the array it returns consist of all the records not only last user record

Edited:

I have also tried while loop as

arr=[]
while arr in row:
   arr= row[0][1]

but when i return this arr , it is empty but if i return row[0][1] then it shows the value of that column.

Thanks in advance.

Answer 1

Assuming that your data is sorted by first 4 entries (which you can do in your SQL), you can transform your data using the following code:

from itertools import groupby
from operator import itemgetter

rows=[
    ('a' , 'b' , 'c' , 'd' , 1),
    ('a' , 'b' , 'c' , 'd' , 2),
    ('z' , 'x' , 'v' , 'n' , 3),
    ('z' , 'x' , 'v' , 'n' , 4)]



out = []
for key,group in groupby(rows, itemgetter(0,1,2,3)):
    new_row = list(key)
    for v in group:
        new_row.append(v[4])
    out.append(new_row)

print out

which prints

[['a', 'b', 'c', 'd', 1, 2], ['z', 'x', 'v', 'n', 3, 4]]

---

Here is another idea for you: use your first 4 entries as keys in a dictionary.

from collections import defaultdict

rows=[
    ('a' , 'b' , 'c' , 'd' , 1),
    ('a' , 'b' , 'c' , 'd' , 2),
    ('z' , 'x' , 'v' , 'n' , 3),
    ('z' , 'x' , 'v' , 'n' , 4)]



d = defaultdict(list)
for r in rows:
    d[tuple(r[0:4])].append(r[4])

print d[('a' , 'b' , 'c' , 'd')]
print d[('z' , 'x' , 'v' , 'n')]

prints

[1, 2]
[3, 4]

With this approach it does not matter if your rows are sorted by first 4 columns