Python 3：醃製和UnPickling類實例返回「沒有持久負載」錯誤

Question

我正在嘗試製作一個程序，收集大量有關當某個樂隊的某些玩家在聖誕節時可用於街拍的數據，而且我正在掙扎讓泡菜功能做我想做...的數據存儲在下面的類的類的實例，Player：

import pickle 

class Player(): 
    def __init__(self, name, instrument, availability): 
     self.Name=name 
     self.Instrument=instrument 
     self.Availability=availability 

的球員名單，PlayerList起初被定義爲一個空列表，我已經定義了一個函數，AddPlayer將初始化一個類實例，並將玩家的詳細信息存儲爲屬性...

PlayerList=[] 

def AddPlayer(PlayerList, name, instrument, availability): 
    NewPlayer = Player(name, instrument, availability) 
    PlayerList.append(NewPlayer) 
    print("Player "+name+" has been added.\n\n") 

我再有，當用戶退出程序存儲的球員名單功能...

def StartProgram(PlayerList): 
    while True: 
     choice=input("Would you like to:\n1 Add a Player?\n2 Quit?\n") 

     if choice=="1":     
     ## Adds the details of the Player using the above function 
      AddPlayer(PlayerList, "Test Player", "Instrument", ["1st Dec AM"]) 
      StartProgram(PlayerList) 

     elif choice=="2": 
      file=open("BuskingList.txt", "wb") 
      file=open("BuskingList.txt", "ab")    
      def AddToList(PlayerList): 
       print("PlayerList: "+str(PlayerList)) 
       HalfPlayerList=PlayerList[:5] 
       ## For some reason, pickle doesn't like me trying to dump a list with more than 
       ## 5 values in it, any reason for that? 

       for Player in HalfPlayerList: 
        print("Player: "+str(Player)) 
        PlayerList.remove(Player) 
        ## Each player removed from original list so it's only added once. 

       print("HalfPlayerList: "+str(HalfPlayerList)) 
       pickle.dump(HalfPlayerList, file) 
       if len(PlayerList) !=0: 
        AddToList(PlayerList) 
        ## Recursive function call while there are still players not dumped 
      AddToList(PlayerList) 
      file.close() 
      quit() 

     else: 
      print("Enter the number 1, 2, or 3.\n") 
      StartProgram(PlayerList) 

和最後在節目開始時的功能運行加載所有玩家的信息。 ..

def Start(): 
    file=open("BuskingList.txt", "rb") 
    print("File contains: "+str(file.readlines())) 
    PlayerList=[] 
    CheckForPlayers=file.read() 
    if CheckForPlayers!="": 
     file=open("BuskingList.txt", "rb") 
     ListOfLists=[] 
     for line in file: 
      ToAppend=pickle.load(file) 
      ListOfLists.append(ToAppend) 
     for ListOfPlayers in ListOfLists: 
      for Player in ListOfPlayers: 
       PlayerList.append(Player) 
     StartProgram(PlayerList) 


print("When entering dates, enter in the form 'XXth Month AM/PM'\n") 
Start() 

當程序第一次運行（提供BuskingList.txt存在），該程序運行正常，添加一個名字的作品和酸洗和退出顯然作品爲之傾倒。然而，在重新啓動程序時，它失敗與下面的錯誤讀取存儲的數據...

File contains: [b'\x80\x03]q\x00c__main__\n', b'Player\n', b'q\x01)\x81q\x02}q\x03(X\x04\x00\x00\x00Nameq\x04X\x0b\x00\x00\x00Test Playerq\x05X\n', b'\x00\x00\x00Instrumentq\x06h\x06X\x0c\x00\x00\x00Availabilityq\x07]q\x08X\n', b'\x00\x00\x001st Dec AMq\tauba.'] 
Traceback (most recent call last): 
    File "I:/Busking/Problem.py", line 63, in <module> 
    Start() 
    File "I:/Busking/Problem.py", line 54, in Start 
    ToAppend=pickle.load(file) 
_pickle.UnpicklingError: A load persistent id instruction was encountered, 
but no persistent_load function was specified. 

我已經做了一些研究，發現這個永久ID說大話不應該是一個問題，爲什麼它出現在這裏？另外，爲什麼酸洗時列表上的五個值會受到限制？任何幫助，將不勝感激。

Answer 1

你先用.readlines()閱讀列表：

print("File contains: "+str(file.readlines())) 

然後再次嘗試閱讀：

CheckForPlayers=file.read() 

這將無法正常工作;文件指針現在位於文件的末尾。倒帶或重新打開文件：

file.seek(0) # rewind to start 

不是說您需要檢查文件內容;讓pickle爲你做到這一點。

接下來由線讀取文件行：

for line in file: 
    ToAppend=pickle.load(file) 

這不工作; pickle格式是二進制，不是面向行的，而你正在通過迭代讀取，然後通過傳入文件對象再次讀取。

離開讀取文件到pickle模塊乾脆：

with open("BuskingList.txt", "rb") as infile: 
    ToAppend=pickle.load(file) 

你還別說在你的代碼：

## For some reason, pickle doesn't like me trying to dump a list with more than 
## 5 values in it, any reason for that? 

味酸有沒有問題任何列表大小，沒有理由把你的球員列表分成五塊。你沒有說明你遇到了什麼問題，但項目在列表中的號碼不能一直的原因：

>>> import pickle 
>>> with open('/tmp/test.pickle', 'wb') as testfile: 
...  pickle.dump(range(1000), testfile) 
... 
>>> with open('/tmp/test.pickle', 'rb') as testfile: 
...  print len(pickle.load(testfile)) 
... 
1000 

此存儲和重新裝載的1000個整數的列表。