Question

可能重复：
What is the equivalent of the C# “using” block in IronPython?

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（我想每个语句都应该检查None） - 如果构造函数失败，变量甚至不存在？）

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()

Answer 1

Python 2.6引入了with语句，该语句在离开with语句时提供对象的自动清理。我不知道IronPython库是否支持它，但它很自然。

具有权威答案的问题：What is the equivalent of the C# "using" block in IronPython?

Answer 2

我认为您正在寻找with statement。更多信息here。

Answer 3

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

Answer 4

您的代码有一些评论：

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()

对于StreamWrite，您可以使用with statment（如果您的对象为 __ 输入 __ 并且 _ 退出 __ 方法）然后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()

和 __ 退出 __ 方法中的StreamWriter

sw.Dispose()

Python相当于C＃的using语句

4 个答案: