student_database.py

students = [["Ben" , {"Maths": 67, "English": 78, "Science": 72}],
            ["Mark", {"Maths": 56, "Art": 64, "History": 39,
            "Geography": 55}],
            ["Paul", {"English": 66, "History": 88}]]

grades = ((0, "FAIL"), (50, "D"), (60, "C"), (70, "B"), (80, "A"), (101, "CHEAT!"))

def print_report_card(report_student=None):
    for student in students:
        if (student [0] == report_student)or (report_student == None) :
            print ("Report card for student ", student [0])
            for subject, mark in student [1].items():
                for grade in grades:
                    if mark  < grade [0]:
                        print (subject, " : ", prev_grade)
                        break
                    prev_grade = grade[1]

def add_student (student_name):
    global students
    for student in students:
        if student[0] == student_name:
            return "Student already in database"
    students.append([student_name, {}])
    return "Student added successfully"

def add_mark (student_name, subject, mark):
    global students
    for student in students:
        if student[0] == student_name:
            if subject in student[1].keys():
                print(student_name, " already has a mark for ",
                  subject)
                user_input = input == ("Overwrite Y/N? ")
                if user_input == "Y" or "y":
                    student[1][subject] = mark
                    return "Student's mark updated"
                else:
                    return "Student's mark not updated"

            else:
                student[1][subject] = mark
                return "Student's mark added"
        return "Students not found"

while True:
    print("Welcome to the Digital Empress Database")
    print("What can I help you with?")
    print("Enter 1 to view all report cards")
    print("Enter 2 to view the report card for a student")
    print("Enter 3 to add a student")
    print("Enter 4 to add a mark to a student")
    print("Enter 5 to exit")

    try:
        user_choice = int (input("Choice: "))
    except ValueError:
        print ("That's not a number I recognize")
        user_choice = 0

    if user_choice == 1:
        print_report_card()
    elif user_choice == 2:
        enter_student = input ("Which student? ")
        print(add_student(enter_student))
    elif user_choice ==3:
        enter_student = input("Student name? ")
        print(add_student(enter_student))
    elif user_choice == 4:
        enter_student = input("Student name? ")
        enter_subject = input("Subject? ")
        num_error = True
        while num_error:
            num_error = False
            try:
                enter_mark = int(input("Mark? "))
            except ValueError:
                print("I dont't recognise that as number")
                num_error = True
        print(add_mark(enter_student, enter_subject, enter_mark))
    elif user_choice == 5:
        break
    else:
        print ("Unknown choice")
    input("Press enter to continue")
print("Goodbye and thank you for using the Raspberry Pi", "Digital Empress Database")