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pythonstringnumpybooleanmapping
Flemingjp
Flemingjp

Reputation: 139

Python - Mapping Strings onto A Boolean Array

I have a boolean array like such

bool_arr = [True, True, False]

And I want to map two Strings onto each boolean value

string_arr = ['r', 'r, 'k']

How would I map this using numpy?

Upvotes: 5

Views: 4916

Answers (3)

Divakar
Divakar

Reputation: 221744

Vectorized approaches using indexing -

bool_arr = np.array([True, True, False]) # Input boolean array
strings = np.array(['k','r']) # Input array of strings for mapping

out = np.take(strings, bool_arr)
out = np.take(strings, bool_arr.astype(int))
out = strings[bool_arr.astype(int)]

Using np.where if we need to choose between just two strings -

np.where(bool_arr, 'r','k')

Upvotes: 4

willeM_ Van Onsem
willeM_ Van Onsem

Reputation: 477794

You can use the numpy.vectorize method:

import numpy as np

x = np.array([True, True, False])
mapping = ('k','r')
result = np.vectorize(lambda i:mapping[i])(x)

which gives:

>>> result
array(['r', 'r', 'k'], 
      dtype='<U1')

Upvotes: 2

timgeb
timgeb

Reputation: 78790

>>> bool_arr = [True, True, False]
>>> ['r' if x else 'k' for x in bool_arr]
['r', 'r', 'k']

Upvotes: 5

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