Este script python funcionou:
import numpy as np
data = np.genfromtxt('inputcsv', delimiter=',')
keys = sorted(set(data[:,0]))
result = np.array([])
for k in keys:
col = data[np.where(data[:,0] == k)][:,1]
if not result.any():
result = col
else:
result = np.vstack((result, col))
print('key {0} finished'.format(k))
np.savetxt('final.csv', np.transpose(result), delimiter=',')