I have tried already for an hour to find a way, but I could only find codes which worked for integers to be changed.
>Solution :
While I cannot read dutch, hopefully you can read English, here it goes.
It seems to me that you would like to replace a letter (thus a string) which is an element of a list. (not sure with another string or an number) so here are possible answers for you.
Say you have a list of words.
a = ["prove","road","load", "car"]
Scenerio one : You want to replace the word "car" with "dog".
[i if i !="car" else "dog" for i in a]
My answer is to go after each members of the list until your condition is met, then replace it.
Scenerio two : You want to replace the word "car" with 10.
[i if i !="car" else 10 for i in a]
Scenerio three : You want the character "o" with "0". (note 0 here is not an interger, but a string.)
[i.replace("o","0") for i in a]
Here you go not just after each members of the list, also each string character of the members, then replace it. Here the replace function specifies String to String only.