Python - 附加到腌制列表

Python - appending to a pickled list

提问by Charlie

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

我正在努力在腌制文件中附加一个列表。这是代码：

#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()

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

我第一次运行代码时，它会打印名称和分数。

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

我第二次运行代码时，它会打印 2 个名称和 2 个分数。

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.

我第三次运行代码时，它会打印第一个名称和分数，但它会用我输入的第三个名称和分数覆盖第二个名称和分数。我只是想让它继续添加名称和分数。我不明白为什么要保存第一个名称并覆盖第二个名称。

采纳答案by dogwynn

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

您需要先从您的数据库（即您的泡菜文件）中提取列表，然后再附加到它。

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)

回答by Mike McKerns

If you want to write and read to the pickled file, you can call dump multiple times for each entry in your list. Each time you dump, you append a score to the pickled file, and each time you load you read the next score.

如果要写入和读取腌制文件，可以为列表中的每个条目多次调用 dump。每次转储时，都会在腌制文件中附加一个分数，每次加载时都会读取下一个分数。

>>> import pickle as dill
>>> 
>>> scores = [('joe', 1), ('bill', 2), ('betty', 100)]
>>> nscores = len(scores)
>>> 
>>> with open('high.pkl', 'ab') as f:
…   _ = [dill.dump(score, f) for score in scores]
... 
>>> 
>>> with open('high.pkl', 'ab') as f:
...   dill.dump(('mary', 1000), f)
... 
>>> # we added a score on the fly, so load nscores+1
>>> with open('high.pkl', 'rb') as f:
...     _scores = [dill.load(f) for i in range(nscores + 1)]
... 
>>> _scores
[('joe', 1), ('bill', 2), ('betty', 100), ('mary', 1000)]
>>>

The reason your code was failing most likely is that you are replacing the original scoreswith the unpickled list of scores. So if there were any new scores added, you'd blow them away in memory.

您的代码失败的最有可能的原因是您正在用scores未腌制的分数列表替换原始代码。因此，如果添加了任何新乐谱，您会在记忆中将它们吹走。

>>> scores
[('joe', 1), ('bill', 2), ('betty', 100)]
>>> f = open('high.pkl', 'wb')
>>> dill.dump(scores, f)
>>> f.close()
>>> 
>>> scores.append(('mary',1000))
>>> scores
[('joe', 1), ('bill', 2), ('betty', 100), ('mary', 1000)]
>>> 
>>> f = open('high.pkl', 'rb')
>>> _scores = dill.load(f)
>>> f.close()
>>> _scores
[('joe', 1), ('bill', 2), ('betty', 100)]
>>> blow away the old scores list, by pointing to _scores
>>> scores = _scores
>>> scores
[('joe', 1), ('bill', 2), ('betty', 100)]

So it's more of a python name reference issue for scores, than it is a pickleissue. Pickleis just instantiating a new list and calling it scores(in your case), and then it garbage collects whatever thing scoreswas pointed to before that.

所以这更像是一个 python 名称引用问题scores，而不是一个pickle问题。 Pickle只是实例化一个新列表并调用它scores（在您的情况下），然后它会垃圾收集scores在此之前指向的任何内容。

>>> scores = 1
>>> f = open('high.pkl', 'rb')
>>> scores = dill.load(f)
>>> f.close()
>>> scores
[('joe', 1), ('bill', 2), ('betty', 100)]

回答by CENTURION

Doesnt actually answer the question, but if anyone would like to add a single item at a time to a pickle, you can do it by...

实际上并没有回答这个问题，但是如果有人想一次向泡菜中添加一个项目，您可以通过...

import pickle
import os

high_scores_filename = '/home/ubuntu-dev/Desktop/delete/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!

names = ["mike", "bob", "joe"]

for name in names:
    high_score = name
    print(name)
    scores.append(high_score)

# 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)

回答by Tessaracter

Don't use pickle but use h5py which also solves your purpose

不要使用pickle，而是使用h5py，这也解决了您的目的

with h5py.File('.\PreprocessedData.h5', 'a') as hf:
    hf["X_train"].resize((hf["X_train"].shape[0] + X_train_data.shape[0]), axis = 0)
    hf["X_train"][-X_train_data.shape[0]:] = X_train_data

    hf["X_test"].resize((hf["X_test"].shape[0] + X_test_data.shape[0]), axis = 0)
    hf["X_test"][-X_test_data.shape[0]:] = X_test_data


    hf["Y_train"].resize((hf["Y_train"].shape[0] + Y_train_data.shape[0]), axis = 0)
    hf["Y_train"][-Y_train_data.shape[0]:] = Y_train_data

    hf["Y_test"].resize((hf["Y_test"].shape[0] + Y_test_data.shape[0]), axis = 0)
    hf["Y_test"][-Y_test_data.shape[0]:] = Y_test_data

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