numpy string operations | index() function

numpy.core.defchararray.index(arr, sub, start=0, end=None) is another function for doing string operations in numpy. It returns the lowest index in the string where substring sub is found for each element in arr. It returns value error if sub is not contained within the range [start, end].

Parameters:
arr : array_like of str or unicode.
sub : [str or unicode] The substring which to be searched.
start : [ int, optional] The starting location in each string.
end : [ int, optional] The ending location in each string.

Returns : [ndarray] Output array of int.

Code #1 :

# Python program explaining
# numpy.char.index() method

# importing numpy
import numpy as geek

# input arrays
in_arr = geek.array(['aAaAaA', 'baA', 'abBABba'])
print ("Input array : ", in_arr)

# output arrays
out_arr = geek.char.index(in_arr, sub ='a')
print ("Output array: ", out_arr)

Output:

Input array :  ['aAaAaA' 'baA' 'abBABba']
Output array:  [0 1 0]

Code #2 :

# Python program explaining
# numpy.char.index() method

# importing numpy
import numpy as geek

# input arrays
in_arr = geek.array(['aAaAaA', 'aA', 'abBABba'])
print ("Input array : ", in_arr)

# output arrays
out_arr = geek.char.index(in_arr, sub ='A', start = 1, end = 4)
print ("Output array: ", out_arr)

Output:

Input array :  ['aAaAaA' 'aA' 'abBABba']
Output array:  [1 1 3]

Code #3 : If substring is not found, raise ValueError.

# Python program explaining
# numpy.char.index() method

# importing numpy
import numpy as geek

# input arrays
in_arr = geek.array(['aAaAaA', 'aA', 'abBABba'])
print ("Input array : ", in_arr)

# output arrays
out_arr = geek.char.index(in_arr, sub ='A', start = 3, end = 7)
print ("Output array: ", out_arr)

Output:

ValueError: substring not found