Version #1

Your programs reads two files, f1 and f2.  It should print all of the items
in f1 that are not in f2, and all items in f2 not in f1.

Your output should look just line the stuff below.

You must use two methods.

Example f1:
a
b
c
1
2
3
d

Example f2:
a
b
c
d
x
y
z

Output:
In file1 but not file2: ['1', '2', '3'].
In file2 but not file1: ['x', 'y', 'z'].