Storing latest 3 scores - SyntaxError: unexpected EOF while parsing

Question

I'm creating a program in Python 3.x where a quiz containing randomly generated simple arithmetic questions (e.g. 3 x 8). The quiz will be played by 3 different classes of school students (not real ones!), and the latest 3 scores of each student should be stored. The scores for each class should be kept separately (in 3 text files).

After the quiz is played by a student, the student's score for that try should be added to their scores.

I created the following code, where filename is the name of the text file which stores the student's class' scores, score is the student's score that they just acheived, fullName is the student's full name (which they inputted at the start), and scores is a dictionary which stores the user's class' scores:

with open(filename, "a+") as file:
    scores = ast.literal_eval(file.read())
#loads student's class' scores into dict

if fullName not in scores:
    scores[fullName] = collections.deque(maxlen=3)
#adds key for student if they haven't played before

scores[fullName].append(score)
#adds student's new score to their scores

with open(filename, "w") as file:
    file.write(str(scores))
#writes updated class scores to student's class' file

But when I run it, I receive an error:

Traceback (most recent call last):
  File "E:\My Documents\Quiz.py", line 175, in <module>
    menu()
  File "E:\My Documents\Quiz.py", line 142, in menu
    scores = ast.literal_eval(file.read())
  File "C:\Python34\lib\ast.py", line 46, in literal_eval
    node_or_string = parse(node_or_string, mode='eval')
  File "C:\Python34\lib\ast.py", line 35, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
  File "<unknown>", line 0

    ^
SyntaxError: unexpected EOF while parsing

I thought that this was because the text files were empty, so when the program tried to read from them, it produced an error. So, I changed it to this:

with open(filename, "a+") as file:
    try:
        scores = ast.literal_eval(file.read())
    except SyntaxError:
        scores = {}
#loads student's class' scores into dict, but if
#text file is empty, it creates empty dict by itself.

if fullName not in scores:
    scores[fullName] = collections.deque(maxlen=3)
#adds key for student if they haven't played before

scores[fullName].append(score)
#adds student's new score to their scores

with open(filename, "w") as file:
    file.write(str(scores))
#writes updated class scores to student's class' file

But when I run the program multiple times, either with different names or with the same name, only the score from the newest try appears. I tried having data already in a text file and then running the program without the try...except statement, but the same SyntaxError still occurred. Why is this happening? Please note that I am a beginner, though, so I may not understand a lot of things.

Answer 1

You could use a deque and pickle but to keep it simple we will use json to dump a dict using lists to hold the values:

# Unless first run for class we should be able to load the dict.

    try:
        with open(filename, "r") as f:
            scores = json.load(f)
    except FileNotFoundError:
        scores = {}

# game logic where you get score...

# try get users list of scores or create new list if it is their first go.
student_list = scores.get(fullName, [])

# if the user has three score remove the oldest and add the new.
# student_list[1:]  takes all but the first/oldest score.
if len(student_list) == 3:
     scores[fullName] = student_list[1:]  + [score]
else:
     # else < 3 so just append the new score.
     student_list.append(score)
     scores[fullName] = student_list


# dump dict to file.
with open(filename, "w") as f:
    json.dump(scores, f)