please use python3 to answer this question:

It must continuously prompt for more user names until a condition, such as typing exit is met.

The company you work for has a policy that says no characters such as #,^% or digits such as 1,2,3,4,5,6,7 are ever used in usernames, and all characters other than letters are filtered (see Version One and Version Two below for further detail).

****At any given time, youre able to see current users.

Comment your code appropriately.

Version One:

A for loop is used to filter out unwanted characters; a STRING is used to store, add, and maintain users.

This is to be referred to as Routine A in your comments.

Version Two:

You must NOT use a for loop. Like Routine A, a STRING is used to store, add, and maintain users.

This is to be referred to as Routine B in your comments.

Version Three:

A for loop is used to filter out unwanted characters; a LIST (array) is used to store, add, and maintain users.

This is to be referred to as Routine C in your comments.

Version Four:

You must NOT use a for loop. Like Routine A, a LIST (array) is used to store, add, and maintain users.

This is to be referred to as Routine D in your comments.

Documentation describing your opinion on the most efficient programming method.