Adding an x to the end of the line of a file.

[Alcanjp]

Hello,

  This is a follow up of the topic posted
https://hashcat.net/forum/thread-10286-p...l#pid53395


  Although I was able to get comprehensive help but I need a different approach. 

I ran this line "hashcat -m 14600 -a 3 -w 3 -1 Xx LUKS_Partition.001 ?l?l?l?l?l?l?l?l?l?1" and I don't have 4600 Years so my next possibility is:
I generated a list of 10.000.000 of 9 Characters Small caps and I need the letter x added to the list.
Notepad ++ crashes
by in Python I have this but it does not write to the file, reads it...

file = open('lines.txt', 'r')
lines = file.readlines()
lines = [line.replace("\n", "") +'x' for line in lines]


And I am looking to get may be,  the Nvidia RTX 3090 GPU to provide me a better chance. 

Appreciate the help.