Convert a list of lists to numpy array in python

Question

I have a list of lists(have tuples inside) and want to convert it to a numpy array.

 Input: 
 [[1, 2, 3, (2, 4)], [3, 4, 8, 9], [2, 3, 5, (3, 7)]]
 Expected output:  
 array([[1, 2, 3, (2, 4)], [3, 4, 8, 9], [2, 3, 5, (3, 7)]])

I have tried np.array and np.asarray, but it raise an error: setting an array element with a sequence. Thanks for your help!

But is `(2, 4)` of `dtype` `int32`? – timgeb Oct 07 '18 at 20:35 — timgeb, Oct 07 '18 at 20:35
oh, i should delete that. dtype is not important for me – Cindy Oct 07 '18 at 20:38 — Cindy, Oct 07 '18 at 20:38

score 0 · Accepted Answer · answered Oct 07 '18 at 21:00

You can set the dtype to object.

>>> import numpy as np
>>> np.array([[1, 2, 3, (2, 4)], [3, 4, 8, 9], [2, 3, 5, (3, 7)]], dtype=object)
array([[1, 2, 3, (2, 4)],
       [3, 4, 8, 9],
       [2, 3, 5, (3, 7)]], dtype=object)

Note that there's probably not a good reason to create this array in the first place. The main strength of numpy is fast operations on flat sequences of numeric data, with dtype=object you are storing pointers to full fledged Python objects - just like in a list.

Here is a good answer explaining the object dtype.

Convert a list of lists to numpy array in python

1 Answers1