Python Lambda函数-列表索引超出范围

Question

I'm new to lambda functions in Python, and I'm trying to work with a CSV file.

My file, eggs.csv, will start off as empty. The intent of the CSV file is to store high scores for a small game I'm building for fun. Each row in the File will include three values: a username, a high score, and a date/time.

What this code does (or rather, should do) is read each row of the CSV, and store each row as its own list. If the CSV has fewer than three rows, it appends a few (for my testing purposes). Each of these lists is then appended to current_scores .

If there are 7 or more rows in current_scores , then it sorts them in descending order based on the 2nd item of the row list (the score). It checks the last item in the current_scores list, and if the player's high_score (hard-coded for now) is higher than the item, then it removes the last item, and appends the new list (which will be a new row in the CSV) with the player score to current_scores .

If there are fewer than seven items in current_scores , the player's info is simply appended. The list is then sorted based on the scores of each list inside it(the 2nd item in the list is the score).

I am using a lambda function to do the sorting, and I get thrown this error when I run it:

C:\Users\kyle\Desktop\csv_workspace>python text_csv.py
[[], ['Kyle', 40, '03/23/2018'], ['Kyle', 41, '03/23/2018'], ['Kyle', 292, '03/23/2018']]
Traceback (most recent call last):
  File "text_csv.py", line 29, in <module>
    current_scores = sorted(current_scores, key=lambda x: x[1], reverse=True)
  File "text_csv.py", line 29, in <lambda>
    current_scores = sorted(current_scores, key=lambda x: x[1], reverse=True)
IndexError: list index out of range

Why is the list index (presumably of the lamba function) out of range? And more importantly, how can I fix it?

See my code below:

user = "Kyle"
high_score = randint(1, 1000)
day = time.strftime("%m/%d/%Y")
with open('eggs.csv', 'r', newline='') as csvfile:
    scores_reader = csv.reader(csvfile, dialect="excel")
    current_scores = []
    for row in scores_reader:
        current_scores.append(row)
    if len(current_scores) < 3:
        for i in range(0, 3):
            current_scores.append(['Kyle', 40+i, day])
    if len(current_scores) >= 7:
        current_scores = sorted(current_scores, key=lambda x: x[1], reverse=True)

        print(current_scores)
        if high_score > int(current_scores[-1][1]): # if player high score is higher than any of current scores
            current_scores.remove(current_scores[-1]) # remove last item in list
            current_scores.append([user, high_score, day]) # append player high score
            current_scores = sorted(current_scores, key= lambda x: x[1], reverse=True)
    else:
        current_scores.append([user, high_score, day])


    print(current_scores)
    current_scores = sorted(current_scores, key=lambda x: x[1], reverse=True)
with open("eggs.csv", 'w', newline="") as csvfile:
    scores_writer = csv.writer(csvfile, dialect="excel")
    for row in current_scores:
        scores_writer.writerow(row)

Answer 1

It looks like you have an empty row at the beginning:

[[], ['Kyle', 40, '03/23/2018'], ['Kyle', 41, '03/23/2018'], ['Kyle', 292, '03/23/2018']]

That first entry, [] doesn't have an element at index 1.