如何在python中使用pickle附加? [英] How to use append with pickle in python?

问题描述

我需要附加到一个pickle文件中(因为我没有一次性带上整个字典).所以为了做同样的事情，我编写了以下代码:

 导入泡菜p={}p[1]=2q={}q['a']=pp={}p[2]=0pickle.dump(q, open("save12.p","ab"))f={}f['b']=ppickle.dump(f,open("save12.p","ab"))

但是，当我加载泡菜文件时，我在那里找不到字典 f 的值??????

有人可以建议我应该如何添加泡菜文件吗???

像dbm"这样的数据库也不能满足我的需要，因为我在 Windows 上工作

解决方案

Pickle 流是完全独立的，因此 unpickling 将一次 unpickle 一个对象.

因此，要对多个流进行 unpickle，您应该反复对文件进行 unpickle，直到出现 EOFError:

<预><代码>>>>f=open('a.p', 'wb')>>>pickle.dump({1:2}, f)>>>pickle.dump({3:4}, f)>>>f.close()>>>>>>f=open('a.p', 'rb')>>>pickle.load(f){1:2}>>>pickle.load(f){3:4}>>>pickle.load(f)回溯(最近一次调用最后一次):文件<stdin>"，第 1 行，在 <module> 中EOF错误

所以你的 unpickle 代码可能看起来像

进口泡菜对象 = []而 1:尝试:objs.append(pickle.load(f))除了EOFError:休息

i need to append to a pickle file (as i don't have the entire dictionary with me at one go). So for doing the same I have written the following code:

 import pickle
 p={}
 p[1]=2
 q={}
 q['a']=p
 p={}
 p[2]=0
 pickle.dump(q, open("save12.p","ab"))
 f={}
 f['b']=p
 pickle.dump(f,open("save12.p","ab"))

However, when I am loading the pickle file I don't find the value of dictionary f there?????

Can someone please suggest as to how should I go about appending in a pickle file???

Also databases like 'dbm' are not working for my need as i am working on windows

解决方案

Pickle streams are entirely self-contained, and so unpickling will unpickle one object at a time.

Therefore, to unpickle multiple streams, you should repeatedly unpickle the file until you get an EOFError:

>>> f=open('a.p', 'wb')
>>> pickle.dump({1:2}, f)
>>> pickle.dump({3:4}, f)
>>> f.close()
>>> 
>>> f=open('a.p', 'rb')
>>> pickle.load(f)
{1: 2}
>>> pickle.load(f)
{3: 4}
>>> pickle.load(f)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
EOFError

so your unpickle code might look like

import pickle
objs = []
while 1:
    try:
        objs.append(pickle.load(f))
    except EOFError:
        break

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