使用Pickle保存分数

Question

我刚接触Python，写了一个程序用来保存高分，使用了一个叫做pickle的字典对象，然后再调用它。我有几个关于我程序的问题，希望有人能帮我解答。

• 如何在多次启动应用时存储和更新这些数据？（退出Python IDLE再重新打开时，这些分数不会被保存）
• 已解决：为什么程序会写入同一个人的新分数，无论是高了还是低了？

-

import pickle

high_scores = {"Adam Smith": 65536, "John Doe": 10000}
with open("highscores.pkl","wb") as out:
    pickle.dump(high_scores, out)

new_score = (raw_input("Enter your name ").title(), int(raw_input("Enter your score ")))

with open("highscores.pkl","rb") as in_:
    high_scores = pickle.load(in_)
if new_score[0] not in high_scores:
    high_scores[new_score[0]] = new_score[1]
if new_score[0] in high_scores and new_score[1] not in high_scores.values():
    high_scores[new_score[0]] = new_score[1] 
else:
    pass

with open("highscores.pkl","wb") as out:
    pickle.dump(high_scores, out)

print("-" * 80)
for name, score in high_scores.items():
    print("{{name:>{col_width}}} | {{score:<{col_width}}}".format(col_width=(80-3)//2).format(name=name, score=score))

Answer 1

为什么程序会写入同一个人的新分数，无论是高还是低？

你并不是在比较分数的大小，而是只是在检查这个分数是否已经存在。

你需要检查一下 if new score is > old score，然后再把它存储到数据里。

你需要先 load 这个对象，然后再进行检查，最后再 dump 数据，否则每次运行程序时都会覆盖掉之前的数据。

high_scores = {"Adam Smith": 65536, "John Doe": 10000}
with open("highscores.pkl","wb") as out:
    pickle.dump(high_scores, out)

每次你启动应用时，都会覆盖掉之前的数据。

在你应用的开头，需要有一些逻辑来检查是否已经有数据被保存，如果没有，那就是第一次运行，所以要设置 high_scores ={}，然后添加更新的信息。如果里面已经有数据了，就要把它解压出来，然后把存储的值和新的值进行比较。

If the file "highscores.pkl" does not exist, high_score ={} else open the file for reading

Do your comparison check and finally pickle.dump to file.

Answer 2

• 使用 `pickle.dump(obj, file)` 可以把对象保存到文件里，而用 `obj = pickle.load(file)` 可以从文件中加载这个对象。看起来你已经做过这些了。
• 试着把 new_score[1] not in high_scores.values() 替换成 new_score[1] > high_scores[new_score[0]]，因为后者实际上是在检查新分数是否比旧分数高。

Answer 3

根据Padraic的建议，下面的代码会先检查一下highscores.pkl这个文件是否存在。如果存在，就把里面的内容读取出来放到high_scores里；如果不存在，就给high_scores赋两个默认的分数。

接下来，当输入一个新分数后，我们会检查一下high_scores里有没有这个玩家的名字（也就是“键”）。如果有，而且新分数比旧分数高，那么就用新分数替换掉旧分数。如果没有这个名字，那就把玩家和分数加进去。

完成这个检查后，high_scores会被保存到highscores.pkl这个文件里。

import pickle
import os

high_scores = {}

if os.path.isfile('highscores.pkl'):
    with open("highscores.pkl", "rb") as f:
        high_scores = pickle.load(f)
else:
    high_scores = {"Adam Smith": 65536, "John Doe": 10000}

new_score = (raw_input("Enter your name ").title(), int(raw_input("Enter your score ")))

if new_score[0] in high_scores:
    if new_score[1] > high_scores[new_score[0]]:
        high_scores[new_score[0]] = new_score[1]
else:
    high_scores[new_score[0]] = new_score[1] 

with open("highscores.pkl","wb") as out:
    pickle.dump(high_scores, out)

print("-" * 80)
for name, score in high_scores.items():
    print("{{name:>{col_width}}} | {{score:<{col_width}}}".format(col_width=(80-3)//2).format(name=name, score=score))