def get_score(who, students, scores):
    '''
    Purpose: Print a student's and their scores.
    Pre:  who is a string.  students is a list of names (strings).
          scores is a list of scores (ints or floats).  students
          and scores are parallel lists.
    Post: returns the score corresponding to the named student.
          If that student was not found, returns 0.
    '''

    result = 0
    if who in students:
        # Find the student
        pos = students.index(who)
        result = scores[pos]
    # Otherwise, result is still zero.
    return result

def get_a_students(students, scores):
    '''
    Purpose: Find students with scores >= 90.
    Pre:  students is a list of names (strings).  scores is a list
          of scores (ints or floats).  students and scores are
          parallel lists.
    Post: returns a new list of the names of those students whose
          scores are greater than or equal to 90.
    '''

    result = []
    for i in range(len(students)):
        if scores[i] >= 90:
            result.append(students[i])
    return result

def main():
    '''Driver program for gradequiz.'''

    students = [ "Doe", "Roe", "Smith", "Jones", "Wang", "Diaz" ]
    scores   = [   75,    88,      93,     83,     78,      94  ]

    print("All students:")
    # Print the scores of all students (in order)
    for st in students:
        sc = get_score(st, students, scores)
        print(st, ":", sc)

    print()

    a_students = get_a_students(students, scores)

    print("Students with 'A's only:")
    for st in a_students:
        sc = get_score(st, students, scores)
        print(st, ":", sc)
    

main()