Python equivalent to C#'s using statement

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

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?)

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()

score 10 · Accepted Answer · edited May 23 '17 at 12:00

10

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.

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

edited May 23 '17 at 12:00

Community

1
1

answered Oct 28 '10 at 12:47

Ned Batchelder

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thanks, that led me to this question: http://stackoverflow.com/questions/1757296/what-is-the-equivalent-of-the-c-using-block-in-ironpython, which somehow I didn't find in my previous searches – Mark Heath Oct 28 '10 at 12:50

score 3 · Answer 2 · answered Oct 28 '10 at 12:50

3

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

answered Oct 28 '10 at 12:50

Damian Schenkelman

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score 0 · Answer 3 · answered Oct 28 '10 at 12:48

0

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.

answered Oct 28 '10 at 12:48

Daniel Roseman

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score 0 · Answer 4 · edited Nov 04 '10 at 12:20

Your code with some comments :

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 :

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

sw.Dispose()

You can also use with statement with IsolatedStorageFile class, if needed. — ohe, Oct 28 '10 at 13:03

Python equivalent to C#'s using statement

4 Answers4

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