python - Counting consecutive duplicates of strings from a list

Question

I have a Python list of strings such that,

Input:

li = ['aaa','bbb','aaa','abb','abb','bbb','bbb','bbb','aaa','aaa']

What can I do to generate another list counting the number of consecutive repetitions of any string in the list? For the list above the return list resembles:

Expected Output:

li_count = [['aaa',1],['bbb',1]['abb',2],['bbb',3],['aaa',2]]

Answer 1

Use itertools.groupby:

from itertools import groupby
li = ['aaa','bbb','aaa','abb','abb','bbb','bbb','bbb','aaa','aaa']

a = [[i, sum(1 for i in group)] for i, group in groupby(li)]
print(a)
[['aaa', 1], ['bbb', 1], ['aaa', 1], ['abb', 2], ['bbb', 3], ['aaa', 2]]

Thank you @user3483203 for improvement:

a = [[i, len([*group])] for i, group in groupby(li)]