Advanced Programming, Jan-Apr 2012
                          Assignment 1
                        27 January, 2012
                      Due 2 February, 2012
              Deadline extended to 4 February, 2012

The academic office at the Hogwarts School of Witchcraft and
Wizardry has compiled data about students' grades.  The data is
in three text files, with the following formatting convention.

1. Information about courses
   File name: courses.txt
   Line format: Course Code~Course Name~Semester~Year~Instructor

2. Information about students
   File name: rollno.txt
   Line format: Roll Number~Full Name

3. Information about grades
   File name: grades.txt
   Line format: Course Code~Semester~Year~Roll Number~Grade

Grades are A, AB, B, BC, C, CD, D with corresponding grade points
10, 9, 8, 7, 6, 5 and 4.  The grade point average of a student is
the sum of his/her grade points divided by the number of courses.
If a student has not completed any courses, the grade point
average is defined to be 0.

Write a Python program to read the data from three files as
described above and generate a file "gpa.txt" listing the grade
point average for each student in the following format:

Roll Number~Full Name~Grade Point Average

Your output should be sorted by Roll Number.

Submit a single Python program called "assignment1.py" (via Moodle).
Sample input data is provided in "hogwarts.zip".

======================================================================