Insert character at a fixed position of lines

[Lie]

On Jul 26, 2:41 pm, "Francesco Pietra" <chiendar... at gmail.com> wrote:
> How to insert letter "A" on each line (of a very long list of lines)
> at position 22, i.e., one space after "LEU", leaving all other
> characters at the same position as in the original example:
>
> ATOM      1  N   LEU     1     146.615  40.494 103.776  1.00 73.04       1SG   2
>
> In all lines"ATOM" is constant as to both position and string, while
> "LEU" is constant as to position only, i.e., "LEU" may be replaced by
> three different uppercase letters. Therefore, the most direct
> indication would be position 22.
>
> Should the script introduce blank lines, no problem. That I know how
> to correct with a subsequent script.
>
> Thanks
> chiendarret

If you want to leave the rest of the strings as-is (i.e. the letter A
overwrites whatever on position 22), Peter's code need to be modified
a little:
line = line[:22] + " " + line[23:]