https://www.reddit.com/r/learnpython/comments/e2c8ud/help_with_really_hard_question_on_making_a_code/

reddit.py

def countAllList(lst):
    # define the list of accumulators:
    counts = [0]*10 
    # counts == [0,0,0...0] length of 10

    # iterate over lst to process each string at a time
    for s in lst:
        # lets turn the string into a list of letters
        s_list = list(s)

        # now count the number of occurances for each digit
        # instead of typing out each digit lets have python
        # do it for us by looping!

        for i in range(10):
            # this loops i from 0 to 9
            # str(i) turns the number into a string

            counts[i] += s_list.count(str(i))

            # since when i == 0, we can kill 2 birds with 1 stone and refer to 
            # counts[i] as the first element of counts. 
            # At the same time we count the occurance of str(i)
            # in our listified string
            # increment i and repeat (i==1, add the result of s_list.count('1') to counts[1] )

    return counts
    
lres = countAllList(["111","2222","009"])
print(lres)

assert countAllList(["111","2222","009"]) == [2, 3, 4, 0, 0, 0, 0, 0, 0, 1]