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

I think you can use groupby with apply tolist with values:

print df.groupby('UserId')['WordID'].apply(lambda x: x.tolist()).values
[[20, 30, 40] [25, 16] [56, 44, 12]]

Or apply list, thank you B.M.

print df.groupby('UserId')['WordID'].apply(list).values
[[20, 30, 40] [25, 16] [56, 44, 12]]

Timings:

df = pd.concat([df]*1000).reset_index(drop=True)

In [358]: %timeit df.groupby('UserId')['WordID'].apply(list).values
1000 loops, best of 3: 1.22 ms per loop

In [359]: %timeit df.groupby('UserId')['WordID'].apply(lambda x: x.tolist()).values
1000 loops, best of 3: 1.23 ms per loop