Data loading using arrays in Python

Question

Have a data in such format in .txt file:

UserId   WordID
  1       20
  1       30
  1       40
  2       25
  2       16
  3       56
  3       44
  3       12
         


        

Answer 1

If you are concerned with performance issues, like often numpy is better :

df=pd.read_csv('file.txt')
def numpyway():
    u,v=df.values.T
    ind=argsort(u,kind='mergesort') # stable sort to preserve order
    return np.split(v[ind],add(1,*where(diff(u[ind]))))


In [12]: %timeit numpyway() # on 8000 lines
10000 loops, best of 3: 250 µs per loop

If 'UserId' is already sorted, it is yet three times faster.