Fix: Resolved list of letters taking up space of code

[drishtisubhedar]

This PR solves the issue where the lists of letters and number are taking up a big amounts of spaces in the code unnecessarily.
This improves the unnecessary use of lines for listing out all of the characters.

Implementation:
Python provides with useful functions like ascii_letters and digits through the string module. So instead of writing the list of letters in so many lines one by one, the function only takes up one line and does the same thing.

Checklist:

• Reduces number of lines for listing letters.
• Considers all the letters and special characters.