ndarray to-string manipulation

Question

I have an ndarray of centroids (k means algorithm) and I want to create a to string for it that turns the ndarray into a string of specific format (shown below) is there an elegant way to do it?

I've tried to play a bit with python's join and split but couldn't quite get the result I wanted.

I wish to turn this:

[[0.7240662  0.64965678 0.55572689]
 [0.50786521 0.43429734 0.35474341]
 [0.04124227 0.03325809 0.04185308]
 [0.19986216 0.17889411 0.17727035]]

Into this:

"[0.72, 0.64, 0.55], [0.50, 0.43, 0.35], [0.04, 0.03, 0.04], [0.19,0.17,0.17]"

Berriel · Accepted Answer · 2019-04-14 14:51:07Z

1

You can use np.array2string(...). There are some examples on the documentation page. It would look like this:

import numpy as np

x = np.random.random((3, 4))
x_str = np.array2string(x, precision=2, separator=', ').replace('\n', '')[1:-1]

print(x)
# [[0.05857399 0.44516104 0.33626309 0.45332413]
#  [0.37389644 0.50240347 0.11313364 0.10669512]
#  [0.38341254 0.52692079 0.1750295  0.44375732]]

print(x_str)
# [0.06, 0.45, 0.34, 0.45], [0.37, 0.5 , 0.11, 0.11], [0.38, 0.53, 0.18, 0.44]

answered Apr 14, 2019 at 14:51

Berriel

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T. Gwen · Accepted Answer · 2019-04-14 14:53:48Z

Ok let's go step by step. Let's call your array a.

>>> a
array([[0.7240662 , 0.64965678, 0.55572689],
       [0.50786521, 0.43429734, 0.35474341],
       [0.04124227, 0.03325809, 0.04185308],
       [0.19986216, 0.17889411, 0.17727035]])

str convert a into string.

>>> str(a)
'[[0.7240662  0.64965678 0.55572689]\n [0.50786521 0.43429734 0.35474341]\n [0.04124227 0.03325809 0.04185308]\n [0.19986216 0.17889411 0.17727035]]'

Then we remove the first and last bracket with a slice.

>>> str(a)[1:-1]
'[0.7240662  0.64965678 0.55572689]\n [0.50786521 0.43429734 0.35474341]\n [0.04124227 0.03325809 0.04185308]\n [0.19986216 0.17889411 0.17727035]'

Then we use replace to format it the way you want.

>>> str(a)[1:-1].replace('\n', ',')
'[0.7240662  0.64965678 0.55572689], [0.50786521 0.43429734 0.35474341], [0.04124227 0.03325809 0.04185308], [0.19986216 0.17889411 0.17727035]'

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