如何檢查一個文件是否已經打開（在同一個進程中）

Question

我想用try catch構造來具體實現。

這related question表明，我可以這樣做：

try: 
    open(fileName, 'wb+') 
except: 
    print("File already opened!") 
    raise 

但是，這是行不通的我。我可以多次打開同一個文件，沒有任何問題：

fileObj1 = open(fileName, 'wb+') 
fileObj2 = open(fileName, 'wb+') 

是因爲我有Python 3.5嗎？或因爲我使用Raspbian？

感謝您的幫助！

Answer 1

您打開相同的文件，但將它們分配給不同的變量。你應該做的是：

fileobj=open(filename,"wb+") 

if not fileobj.closed: 
    print("file is already opened")` 

我正在用我的手機寫，所以造型可能不好，但你會明白的。順便說一下，.closed只檢查文件是否已被相同的python進程打開。

Answer 2

我會建議使用這樣的東西。

def is_open(file_name): 
    if os.path.exists(file_name): 
     try: 
      os.rename(file_name, file_name) #can't rename an open file so an error will be thrown 
      return False 
     except: 
      return True 
    raise NameError 

編輯以適應OP的具體問題

class FileObject(object): 
    def __init__(self, file_name): 
     self.file_name = file_name 
     self.__file = None 
     self.__locked = False 

    @property 
    def file(self): 
     return self.__file 

    @property 
    def locked(self): 
     return self.__locked 

    def open(self, mode, lock=True):#any testing on file should go before the if statement such as os.path.exists() 
     #replace mode with *args if you want to pass multiple modes 
     if not self.locked: 
      self.__locked = lock 
      self.__file = open(self.file_name, mode) 
      return self.file 
     else: 
      print 'Cannot open file because it has an exclusive lock placed on it' 
      return None #do whatever you want to do if the file is already open here 

    def close(self): 
     if self.file != None: 
      self.__file.close() 
      self.__file = None 
      self.__locked = False 

    def unlock(self): 
     if self.file != None: 
      self.__locked = False