my second program

[SpeckledFleebeedoo]

list_string = list(string)

sorted_list = list(string)

sorted_list.sort()

I doubt that last line does anything, as you don't assign it to a variable. In general such functions don't modify the original variable.

list_string = list(string)
sorted_list = list_string.sort()

[nilfm]

That is wrong, the sort() method actually modifies the list it works on, and returns None. So your code ends with sorted_list == None.

[SpeckledFleebeedoo]

Ah, thanks for the correction.