Python相当于C＃的using语句[duplicate]

Possible Duplicate:
What is the equivalent of the C# “using” block in IronPython?

可能重复：IronPython中C＃“using”块的等价物是什么？

I'm writing some IronPython using some disposable .NET objects, and wondering whether there is a nice "pythonic" way of doing this. Currently I have a bunch of finally statements (and I suppose there should be checks for None in each of them too - or will the variable not even exist if the constructor fails?)

我正在使用一些一次性.NET对象编写一些IronPython，并想知道是否有一种很好的“pythonic”方式。目前我有一堆finally语句（我想在每个语句中都应该检查None）或者如果构造函数失败，变量是否甚至不存在？）

def Save(self):
    filename = "record.txt"
    data = "{0}:{1}".format(self.Level,self.Name)
    isf = IsolatedStorageFile.GetUserStoreForApplication()
    try:                
        isfs = IsolatedStorageFileStream(filename, FileMode.Create, isf)
        try:
            sw = StreamWriter(isfs)
            try:
                sw.Write(data)
            finally:
                sw.Dispose()
        finally:
            isfs.Dispose()
    finally:
        isf.Dispose()

4 个解决方案

#1

Python 2.6 introduced the with statement, which provides for automatic clean up of objects when they leave the with statement. I don't know if the IronPython libraries support it, but it would be a natural fit.

Python 2.6引入了with语句，它提供了在离开with语句时自动清理对象。我不知道IronPython库是否支持它，但它很自然。

Dup question with authoritative answer: What is the equivalent of the C# "using" block in IronPython?

具有权威性答案的Dup问题：IronPython中C＃“using”块的等价物是什么？

#2

I think you are looking for the with statement. More info here.

我想你正在寻找with声明。更多信息在这里。

#3

If I understand correctly, it looks like the equivalent is the with statement. If your classes define context managers, they will be called automatically after the with block.

如果我理解正确，看起来等效于with语句。如果您的类定义了上下文管理器，那么它们将在with块之后自动调用。

#4

Your code with some comments :

你的代码有一些评论：

def Save(self):
    filename = "record.txt"
    data = "{0}:{1}".format(self.Level,self.Name)
    isf = IsolatedStorageFile.GetUserStoreForApplication()
    try:                
        isfs = IsolatedStorageFileStream(filename, FileMode.Create, isf)

        try: # These try is useless....
            sw = StreamWriter(isfs)
            try:
                sw.Write(data)
            finally:
                sw.Dispose()
        finally: # Because next finally statement (isfs.Dispose) will be always executed
            isfs.Dispose()
    finally:
        isf.Dispose()

For StreamWrite, you can use a with statment (if your object as __enter__ and _exit__ methods) then your code will looks like :

对于StreamWrite，您可以使用with statment（如果您的对象为__enter__和_exit__方法），那么您的代码将如下所示：

def Save(self):
    filename = "record.txt"
    data = "{0}:{1}".format(self.Level,self.Name)
    isf = IsolatedStorageFile.GetUserStoreForApplication()
    try:                
        isfs = IsolatedStorageFileStream(filename, FileMode.Create, isf)
        with StreamWriter(isfs) as sw:
            sw.Write(data)
    finally:
        isf.Dispose()

and StreamWriter in his __exit__ method has

和他的__exit__方法中的StreamWriter有

sw.Dispose()

#1