Monday, October 26, 2009

Improvements to Try Python: File I/O

Try Python is an online Python tutorial that has an interactive interpreter running in the browser through the magic of Silverlight and IronPython.

Try Python presents the Python tutorial, with executable code examples for you to try out. However, because Silverlight is a sandboxed browser plugin, with no access to the local filesystem, the parts of the tutorial that do file I/O didn't work.

I've fixed that by reimplementing the file type (and swapping out the builtin file type and open function) in pure Python using local browser storage to store files. You can now create files from the interpreter and read them back in in exactly the same way you do in standard Python on the desktop.

This pure Python implementation of file also has other potential uses, for example unit testing filesystem access.
A few weeks ago I announced Try Python, a Python tutorial with interactive interpreter that runs in the browser using IronPython and Silverlight.

Because it runs in Silverlight, which is sandboxed from the local system, the parts of the tutorial that show how to do file I/O didn't work. I've finally fixed this with a pretty-much-complete implementation of the file type and open function that use local browser storage (IsolatedStorage) to store the files.

You can try this out by going direct to the Reading and Writing Files part of the tutorial (page 32).
The implementation is split into two parts, the file type and open function in and the backend that uses the IsolatedStorage API in There are also extensive tests of course.
So in my last blog entry I introduced and discussed how it could simply testing file access. What I didn't do is show you how.

In writing this example I realised an added benefit; it can remove the differences between platforms.

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