def average_grade(grade_list):
    '''Return the average grade (a float) for all of the students in the 
    list of lists grade_list, where the inner lists contain a student ID 
	(a str) and a grade (a number).'''
    
    total_grade = 0.0
    
    for student in grade_list:
        total_grade = total_grade + student[1]

    return total_grade / len(grade_list)

def get_student_IDs(grade_list):
    '''Return a list of strs containing the student IDs from the list of lists
    grade_list, where the inner lists contain a student ID (a str) and a grade
    (a number).'''
    
    ID_list = []

    for student in grade_list:
        ID_list.append(student[0])

    return ID_list


if __name__ == '__main__':

    student_grades = [['999888777', 78], ['111222333', 90], ['444555666', 83]]

    a = average_grade(student_grades)
    print "About to print the average of the student grades in"
    print student_grades
    print "which is a list of lists, where each inner list"
    print "contains a student number and a grade"
    print a, "should be",83.666666666666671
    raw_input("Enter 1 to move on ")

    ids = get_student_IDs(student_grades)
    print "About to print a list of only the student ids"
    print ids, "should be", ['999888777', '111222333', '444555666']