summarize a string in 3 different ways

summarize_string.py

from itertools import groupby
import numpy as np

def summarize_string1(s):
    if not s:
        return []
    return [(0,s[0])]+[(i, c) for (i, (c, pc)) in enumerate(zip(s[1:],s),1) if c != pc]
  
def summarize_string2(s):
    result = []
    for letter, group in groupby(enumerate(s),lambda x: x[1]):
        result.append(next(group))
    return result
  
def summarize_string3(s):
    str_arr = np.array(list(s.encode('ascii')))
    loc = np.diff(str_arr,prepend=0).nonzero()[0]
    return [(i, s[i]) for i in loc]

# summarize_string('hhhhhhhaaaaaaaabbbbbbbvvvvvaaaahhhh')
# [(0, 'h'), (7, 'a'), (15, 'b'), (22, 'v'), (27, 'a'), (31, 'h')]