Remove the fixed-size constraint in numpy fixed-size array

Question

I have now a fixed-size string numpy array:

import numpy as np

str_arr = np.array(['test1', 'test2'], dtype='<U5')
str_arr[0] = 'longer_string'
print(str_arr)

And it returns

['longe' 'test2']

I'd like to remove this limit. Would there be a way to do so? Below is an example of my failed attempt:

str_arr_copy = str_arr.astype(str)
str_arr_copy[0] = 'longer_string'
print(str_arr_copy)

And it doesn't help at all.

Thank you!

str_arr.astype('U100') gives you more space, but doesn't eliminate the limit. For this work a regular list is probably better. — hpaulj
– hpaulj, Commented Apr 11, 2017 at 21:44

jakevdp · Accepted Answer · 2017-04-11 21:21:48Z

2

You could convert it to dtype=object, do the assignment, and then convert back to dtype=str:

>>> str_arr_copy = str_arr.astype(object)
>>> str_arr_copy[0] = 'longer_string'
>>> print(str_arr_copy.astype(str))
array(['longer_string', 'test2'], 
      dtype='<U13')

answered Apr 11, 2017 at 21:21

jakevdp

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1 Comment

hpaulj Over a year ago

Using arr.tolist() to generate the intermediate copy runs in about the same time.

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