The function xf has multiple variables as input. One of them is a string KeyOpt and one of them is an integer n. This illustrates that the input variable can be not only a simple numeric variable but also a string, float, integer, array.. etc.
The if condition inside the function. If the string keyOpt == 'Yes' than assign the value x and y to be these arrays. If on the other the value of keyOpt == 'No' than assign the value of x and y to be these arrays. A reminder that you used two == signs not one = for the equal operator (Lab03-Ex2).
The value of the string can be used in the function xf either by using ' ' or " ". Note that it is case sensetive.
x1,y1 = xf('Yes',150)
Also note that the output here is multiple arrays x and y which are read by simply assigning them to the arrays x1 and y1.
Note that the output not only can be multiple variables but can also be arrays, string, integers, simple variables...etc