Why is there a range error in the for loop?

def frequency_analysis(string):
    count = 0
    freq_list = [
        [[" "] * len(string)],
        []
        ]
    print(freq_list[0])
    for i in range(len(string)):
        print(i)
        freq_list[0][i] = string[i]
        print(freq_list[0])
    return freq_list
print(frequency_analysis("fhfhffffj"))
print(frequency_analysis("jfjf"))

This is for a school assignment and I am not allowed to use built in functions other than len(). I am trying to make the freq_list[0] a list of separate characters from the string input. For some reason, after the first switch it turns the first list created into a list of just one item and then there is an out of range error. Can anyone explain why this is happening.

Input "fhh"
prints:

[" "," "," "]
0
"f"
1
Error

>Solution :

At freq_list[0], your are creating a nested list. You should either declare it with

freq_list = [
    [" "] * len(string),
    []
    ]

if the nesting is unwanted, or assign values in it with

freq_list[0][0][i] = string[i]

Here, with the two [0] indexing, you do access the inner list which you originally want to assign values within.