附加到pickle文件而不删除

Question

我试着用pickle模块写入使用二进制模式的文件。这是一个例子：

import pickle 
    file = open("file.txt","wb") 
    dict = {"a":"b","c":"d"} 
    pickle.dump(dict, file) 
    file.close() 

但是这种方法删除了之前写的其他字典。如何在不删除文件中的其他内容的情况下编写代码？

Answer 1

你需要附加到原始文件，但首先取消内容（我假设原始文件已酸洗内容）。 什么你做的是简单地覆盖了新腌制的对象

import pickle 

#create the initial file for test purposes only 
obj = {"a":"b","c":"d"} 
with open("file.txt","wb") as f: 
    pickle.dump(obj, f) 

#reopen and unpickle the pickled content and read to obj 
with open("file.txt","rb") as f: 
    obj = pickle.load(f) 
    print(obj) 

#add to the dictionary object 
obj["newa"]="newb" 
obj["newc"]="newd" 

with open("file.txt","wb") as f: 
    pickle.dump(obj, f) 

#reopen and unpickle the pickled content and read to obj 
with open("file.txt","rb") as f: 
    obj = pickle.load(f) 
    print(obj) 

Answer 2

您可以在一个文件中串联腌制对象的现有文件，所以没有必要读取该文件，并改写它。你只需要附加到文件，而不是覆盖它。

替换：

file = open("file.txt","wb") 

有了：

file = open("file.txt","ab") 

有关可用的文件模式和他们所做的事情，看到documentation的更多信息。

请记住，您需要多个pickle.load()才能取消数据。