Answer 1

If you mean simply storing the value for use in the script, it would be a matter of storing the input in a variable.
var = input ()

Else if you mean executing the value that has been input, use the eval () function. It evaluates an argument as if it were a statement.
eval(input ())
Say if the user input print (2+2), it would evaluate the input as a statement and execute it, therefore printing 4.
If the user input a string to delete their C drive, the script would delete their C drive(if the script had admin permissions).
So be careful with how you use it. If this is not what you meant, please elaborate.