Convert elements in a numpy array to string

Question

I wrote the following script to load data from CSV file in numpy array form:

import numpy

sample = numpy.genfromtxt('sample_cor.csv', delimiter = ',')
print sample

and this sample looked like:

[[  259463.392   2737830.062 ]
 [  255791.4823  2742050.772 ]
 [  249552.4949  2746152.328 ]
 [  247925.1228  2746422.143 ]
 [  262030.4697  2728966.229 ]
 [  260462.1936  2731412.856 ]
 [  260644.0281  2735003.027 ]
 [  268588.7974  2732835.097 ]]

now I want to extract every row in this array to string with a comma, for example, I expected row 1 to be converted to 259463.392,2737830.062, row 2 to be 255791.4823,2742050.772, and so on.

I tried the code below:

ss = numpy.array_str(sample[0])
print ss
print type(ss)

and got the result maybe not what I want,

[  259463.392  2737830.062]
<type 'str'>

(I used coords = '259467.2,2737833.87' and got the string form which was what I want: 259467.2,2737833.87)

How to convert elements in a numpy array to string with a comma?

The form without the , is just the normal way that numpy arrays are displayed. It helps distinguish them from Python lists. The , is not an integral part of either a list or an array. It's just a display feature. — hpaulj
– hpaulj, Commented Oct 26, 2016 at 17:59

Divakar · Accepted Answer · 2016-10-26 12:11:35Z

18

Here's an approach using join method -

[",".join(item) for item in a.astype(str)]

Sample run -

In [141]: a
Out[141]: 
array([[  259463.392 ,  2737830.062 ],
       [  255791.4823,  2742050.772 ],
       [  249552.4949,  2746152.328 ],
       [  247925.1228,  2746422.143 ],
       [  262030.4697,  2728966.229 ],
       [  260462.1936,  2731412.856 ],
       [  260644.0281,  2735003.027 ],
       [  268588.7974,  2732835.097 ]])

In [142]: [",".join(item) for item in a.astype(str)]
Out[142]: 
['259463.392,2737830.062',
 '255791.4823,2742050.772',
 '249552.4949,2746152.328',
 '247925.1228,2746422.143',
 '262030.4697,2728966.229',
 '260462.1936,2731412.856',
 '260644.0281,2735003.027',
 '268588.7974,2732835.097']

answered Oct 26, 2016 at 12:11

Divakar

222k19 gold badges273 silver badges374 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Heinz Over a year ago

thank you for the advice, but I have a little question that why the showing of mine of numpy array in the post lack comma?

Divakar Over a year ago

@Heinz Hmm if the input is a NumPy array, it should. Or else, you could try print(repr(a)).

Heinz Over a year ago

Thank you, repr() returns the having-comma array.

fazistinho_ Over a year ago

@Divakar is there a "pure" numpy solution to this and would that make it faster for large datasets? Thank you

Rishabh Barman Over a year ago

I am very late to the party, though! hey @Heinz, since you're printing that Numpy array via print(), it doesn't display the commas. Try simply running the variable in a single Jupyter cell - then, elements display with commas.

Collectives™ on Stack Overflow

Convert elements in a numpy array to string

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related