附加到pickle文件而不刪除

Question

我試着用pickle模塊寫入使用二進制模式的文件。這是一個例子：

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

但是這種方法刪除了之前寫的其他字典。如何在不刪除文件中的其他內容的情況下編寫代碼？

Answer 1

你需要附加到原始文件，但首先取消內容（我假設原始文件已酸洗內容）。 什麼你做的是簡單地覆蓋了新醃製的對象

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

您可以在一個文件中串聯醃製對象的現有文件，所以沒有必要讀取該文件，並改寫它。你只需要附加到文件，而不是覆蓋它。

替換：

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

有了：

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

有關可用的文件模式和他們所做的事情，看到documentation的更多信息。

請記住，您需要多個pickle.load()才能取消數據。