保存和加载对象以及使用泡菜 [英] Saving and loading objects and using pickle

问题描述

我正在尝试使用pickle模块保存和加载对象.
首先，我声明我的对象:

I´m trying to save and load objects using pickle module.
First I declare my objects:

>>> class Fruits:pass
...
>>> banana = Fruits()

>>> banana.color = 'yellow'
>>> banana.value = 30

此后，我打开一个名为"Fruits.obj"的文件(以前我创建了一个新的.txt文件，并将其重命名为"Fruits.obj"):

After that I open a file called 'Fruits.obj'(previously I created a new .txt file and I renamed 'Fruits.obj'):

>>> import pickle
>>> filehandler = open(b"Fruits.obj","wb")
>>> pickle.dump(banana,filehandler)

完成此操作后，我关闭了会话，开始了一个新会话，然后放入下一个会话(尝试访问应该保存的对象):

After do this I close my session and I began a new one and I put the next (trying to access to the object that it supposed to be saved):

file = open("Fruits.obj",'r')
object_file = pickle.load(file)

但是我收到此消息:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Python31\lib\pickle.py", line 1365, in load
encoding=encoding, errors=errors).load()
ValueError: read() from the underlying stream did notreturn bytes

我不知道该怎么办，因为我不了解此消息. 有人知道如何加载对象"banana"吗? 谢谢！

I don´t know what to do because I don´t understand this message. Does anyone know How I can load my object 'banana'? Thank you!

正如你们中的一些人所说的那样:

As some of you have sugested I put:

>>> import pickle
>>> file = open("Fruits.obj",'rb')

没有问题，但是我要讲的是:

There were no problem, but the next I put was:

>>> object_file = pickle.load(file)

我有错误:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Python31\lib\pickle.py", line 1365, in load
encoding=encoding, errors=errors).load()
EOFError

推荐答案

关于第二个问题:

 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "C:\Python31\lib\pickle.py", line
 1365, in load encoding=encoding,
 errors=errors).load() EOFError

读取文件的内容之后，文件指针将位于文件的末尾-将不再读取其他数据.您必须倒带该文件，以便从头开始再次读取该文件:

After you have read the contents of the file, the file pointer will be at the end of the file - there will be no further data to read. You have to rewind the file so that it will be read from the beginning again:

file.seek(0)

您通常要做的是使用上下文管理器打开文件并从中读取数据.这样，在块执行完后文件将自动关闭，这也将帮助您将文件操作组织为有意义的块.

What you usually want to do though, is to use a context manager to open the file and read data from it. This way, the file will be automatically closed after the block finishes executing, which will also help you organize your file operations into meaningful chunks.

最后，cPickle是C语言中的pickle模块的更快实现.

Finally, cPickle is a faster implementation of the pickle module in C. So:

In [1]: import cPickle

In [2]: d = {"a": 1, "b": 2}

In [4]: with open(r"someobject.pickle", "wb") as output_file:
   ...:     cPickle.dump(d, output_file)
   ...:

# pickle_file will be closed at this point, preventing your from accessing it any further

In [5]: with open(r"someobject.pickle", "rb") as input_file:
   ...:     e = cPickle.load(input_file)
   ...:

In [7]: print e
------> print(e)
{'a': 1, 'b': 2}

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