Numpy: How to cast string array to float while some of the elements contain extra quoted string

Question

I am trying to convert string to float type by the following

X = arr[:,:-1].astype(np.float32)

However, error as below is rising

ValueError: could not convert string to float: '"53"'

I know this means I have some elements with extra quote in the array. My problem is how should I solve this. How can I convert element '"53"' into 53 inside the array?

UPDATE 1: Here is an example to reproduce

import numpy as np
a = np.array([['12','13'],['"53"','44']])
a = a.astype(np.float32)

It would be nice if you could provide a reproducible example. — Mad Physicist
– Mad Physicist, Commented Nov 14, 2018 at 5:17

Riley Steele Parsons · Accepted Answer · 2018-11-14 05:12:54Z

4

Try stripping the double quotes from the array, then casting to float.

Like so:

arr = np.char.strip(arr, '"')
X = arr[:,:-1].astype(np.float32)

edited Nov 14, 2018 at 5:12

answered Nov 14, 2018 at 5:07

Riley Steele Parsons

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Nirmal · Accepted Answer · 2018-11-14 06:02:27Z

1

You could also use numpy.char.replace() to perform element-wise string replace on an array of strings.

Signature: np.char.replace(a, old, new, count=None)

Docstring: For each element in a, return a copy of the string with all occurrences of substring old replaced by new. Calls str.replace element-wise.

import numpy as np
a = np.array([["12","13"],['"53"',"44"]])

b = np.char.replace(a, '"', '')
c = b.astype(np.float32)

answered Nov 14, 2018 at 6:02

Nirmal

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