Is it possible to find the index of elements with char value higher than `n` with numpy?

Basically I have something like this :

letters = "ABNJDSJHIUOIUIYEIUWEYIUJHAJHSGJHASNMVFDJHKIUYEIUWYEWUIEYUIUYIEJSGCDJHDS"

And I want to find the index of letters above let’s say M. I want to do something like :

import numpy as np

letters = "ABNJDSJHIUOIUIYEIUWEYIUJHAJHSGJHASNMVFDJHKIUYEIUWYEWUIEYUIUYIEJSGCDJHDS"

# - test
np_array = np.array(np.where(letters > chr(77))[0])

Is this possible? or do I have do something like letters not in ...?

>Solution :

Convert letters to a character array:

>>> ar = np.array(list(letters))
>>> ar
array(['A', 'B', 'N', 'J', 'D', 'S', 'J', 'H', 'I', 'U', 'O', 'I', 'U',
       'I', 'Y', 'E', 'I', 'U', 'W', 'E', 'Y', 'I', 'U', 'J', 'H', 'A',
       'J', 'H', 'S', 'G', 'J', 'H', 'A', 'S', 'N', 'M', 'V', 'F', 'D',
       'J', 'H', 'K', 'I', 'U', 'Y', 'E', 'I', 'U', 'W', 'Y', 'E', 'W',
       'U', 'I', 'E', 'Y', 'U', 'I', 'U', 'Y', 'I', 'E', 'J', 'S', 'G',
       'C', 'D', 'J', 'H', 'D', 'S'], dtype='<U1')
>>> np.where(ar > 'M')[0]
array([ 2,  5,  9, 10, 12, 14, 17, 18, 20, 22, 28, 33, 34, 36, 43, 44, 47,
       48, 49, 51, 52, 55, 56, 58, 59, 63, 70], dtype=int64)

Byte arrays can also be:

>>> ar = np.array(bytearray(letters.encode()))
>>> ar
array([65, 66, 78, 74, 68, 83, 74, 72, 73, 85, 79, 73, 85, 73, 89, 69, 73,
       85, 87, 69, 89, 73, 85, 74, 72, 65, 74, 72, 83, 71, 74, 72, 65, 83,
       78, 77, 86, 70, 68, 74, 72, 75, 73, 85, 89, 69, 73, 85, 87, 89, 69,
       87, 85, 73, 69, 89, 85, 73, 85, 89, 73, 69, 74, 83, 71, 67, 68, 74,
       72, 68, 83], dtype=uint8)
>>> np.where(ar > ord('M'))[0]
array([ 2,  5,  9, 10, 12, 14, 17, 18, 20, 22, 28, 33, 34, 36, 43, 44, 47,
       48, 49, 51, 52, 55, 56, 58, 59, 63, 70], dtype=int64)