convert python list to numpy array boolean

Question

I have a big list in python like small example and want to make a numpy array which is boolean.

small example:

li = ['FALSE', 'FALSE', 'TRUE', 'FALSE', 'FALSE', 'FALSE']

I tried to change it using the following line:

out = array(li, dtype = bool)

and then I got this output:

out = array([ True, True, True, True, True, True], dtype=bool)

but the problem is that they are all True. how can I make the same array but elements should remain the same meaning False should be False and True should be True in the new array.

Moses Koledoye · Accepted Answer · 2017-04-26 12:59:48Z

4

You can convert the strings to boolean literals using str.title and ast.literal_eval:

import ast
import numpy as np

li = ['FALSE', 'FALSE', 'TRUE', 'FALSE', 'FALSE', 'FALSE']
arr = np.array([ast.literal_eval(x.title()) for x in li])
# array([False, False,  True, False, False, False], dtype=bool)

You could otherwise use a simple list comprehension if you have only those two in your list:

arr = np.array([x=='TRUE' for x in li])
# array([False, False,  True, False, False, False], dtype=bool)

Keep in mind that non-empty strings are truthy, so coercing them to bool like you did will produce an array with all elements as True.

edited Apr 26, 2017 at 12:59

answered Apr 26, 2017 at 12:49

Moses Koledoye

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Comments

akash karothiya · Accepted Answer · 2017-04-26 12:57:47Z

4

bool('True') and bool('False') always return True because strings 'True'and 'False' are not empty

You can create afunction to convert string to bool

def string_to_bool(string):
    if string == 'True':
        return True
    elif string == 'False':
        return False
>>> string_to_bool('True')
True

edited Apr 26, 2017 at 12:57

answered Apr 26, 2017 at 12:42

akash karothiya

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2 Comments

ARM Over a year ago

then what is the solution to get the output i WANT

Christian König Over a year ago

elif s should be elif string Also to be compatible with OPs data, the comparison should be to 'TRUE' and 'FALSE'.

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