Column xyz data to grid for plotting
x y z

1 1 10

1 2 12

2 1 14

2 2 16

10 12

14 16

import numpy

idx1 = numpy.array([0, 0, 1, 1])
idx2 = numpy.array([0, 1, 0, 1])
data = numpy.array([10, 12, 14, 16])

grid = numpy.zeros(len(data)/2, 2)
grid[idx1, idx2] = data

>>>grid
array([[ 10.,  12.],
      [ 14.,  16.]])

data.txt
x y z
1 1 10
1 2 12
2 1 14
2 2 16

def extract(filepath):
    f = open(filepath)
    f.readline() # to read out the first line that says "x y z"
    while 1:
        x = f.readline().strip().split()[-1]
        y = f.readline().strip().split()[-1]
        print x, y

data.txt
x y z
1 1 10
2 1 14
1 2 12
2 2 16

from collections import defaultdict
def extract(filepath):
    coords = defaultdict(dict)
    f = open(filepath)
    f.readline() # to read out the first line that says "x y z"
    for line in f:
        id, axis, val = map(int, line.strip().split())
        coords[id][axis] = val

    for i in sorted(coords):
        print coords[i][1], coords[i][2]