Python-附加到腌制列表

问题描述：

我正在努力将列表添加到腌制文件中. 这是代码:

I'm struggling to append a list in a pickled file. This is the code:

#saving high scores to a pickled file

import pickle

first_name = input("Please enter your name:")
score = input("Please enter your score:")

scores = []
high_scores = first_name, score
scores.append(high_scores)

file = open("high_scores.dat", "ab")
pickle.dump(scores, file)
file.close()

file = open("high_scores.dat", "rb")
scores = pickle.load(file)
print(scores)
file.close()

我第一次运行代码时，它会打印名称和分数.

The first time I run the code, it prints the name and score.

第二次运行代码时，它将打印2个名称和2个分数.

The second time I run the code, it prints the 2 names and 2 scores.

第三次运行代码时，它会打印出名字和分数，但是会用我输入的第三个名字和分数来覆盖第二个名字和分数.我只希望它继续添加名称和分数.我不明白为什么要保存名字并覆盖第二个名字.

The third time I run the code, it prints the first name and score, but it overwrites the second name and score with the third name and score I entered. I just want it to keep adding the names and scores. I don't understand why it is saving the first name and overwriting the second one.

答

您需要先从数据库(即泡菜文件)中提取列表，然后再附加到列表中.

You need to pull the list from your database (i.e. your pickle file) first before appending to it.

import pickle
import os

high_scores_filename = 'high_scores.dat'

scores = []

# first time you run this, "high_scores.dat" won't exist
#   so we need to check for its existence before we load 
#   our "database"
if os.path.exists(high_scores_filename):
    # "with" statements are very handy for opening files. 
    with open(high_scores_filename,'rb') as rfp: 
        scores = pickle.load(rfp)
    # Notice that there's no "rfp.close()"
    #   ... the "with" clause calls close() automatically! 

first_name = input("Please enter your name:")
score = input("Please enter your score:")

high_scores = first_name, score
scores.append(high_scores)

# Now we "sync" our database
with open(high_scores_filename,'wb') as wfp:
    pickle.dump(scores, wfp)

# Re-load our database
with open(high_scores_filename,'rb') as rfp:
    scores = pickle.load(rfp)

print(scores)

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