Reading CSV files in IronPython

This is in continuation with my previous blog post :

To get IronPython to use Standard Python Modules,  one needs to add the following two lines to C:\IronPython-2.0.1\Lib\site.py :

import sys
sys.path.append(r"C:\Python25\Lib")

While this works for most part, it doesn’t help if you are using Python extensions written in C. More about my specific problems in another post. But there is an open source project IronClad to deal specifically with this issue. In the meantime, you can check the differences between IronPython and CPython

Reading (and writing to) CSV file is critical part of my program, while in stadard python it was as easy as “import csv”, the same thing took some efforts to get it working in IronPython. I got the following error for my import statement

Error on line 7 in csv.py
from functools import reduce

I also tried using ActiveState Python 2.5.2.2 (which I already had from few months ago, didn’t feel like downloading the latest version till the problem was fixed) But that didn’t help either. With ActiveState, I got the same error on the same line, except this time it was for _csv.

To Quote from IronPython Cookbook :

For some reason the Python standard library csv module is written in C, which means that it isn’t available to IronPython.

The cookbook points to a third party library called A Fast Csv Reader . The cookbook has a nice example of how to use the said DLL with your IronPython Program.

It wasn’t clear to me as to why I had to register at Code Project to download this binary since it is provided under MIT Open Source License. But whom am I gonna complain to ? Beggars can’t be choosers

IronPython

After working on initial prototype using pylons, on ubuntu, my employer needed a standalone application (on windows) So I was looking for ways to reuse my python code to avoid double work.  had only heard about iron python but beyond that I did not know anything more.

A bit of research later, I downloaded IronPython from here and IronPython Studio. I was quite thrilled to find out that Microsoft, has created this shell, which allows developers to integrate new languages with Visual Studio Shell.

Installing IronPython Studio

Installing IronPython was very straight forward. Considering it is one of the Python implementation itself, you don’t have to have standard python installed. (But I did, more on that later)

Setting up IronPython Studio wasn’t so straight forward.  I had to download standalone version of Visual Studio shell. But the problem, and it is well documented, is that installing the redistributable package in itself is not the complete step, as you would believe from the website. I confirmed that the package was installed, and stil IronPython Studio would complain, and refuse to proceed. It turns out that you need to install the Visual Studio environment, which is inside this directory structure you just created.

Once I installed Visual Studio Shell, IronPython Studio installed easily.  Using IronPython has been nice experience in just a few hours I have been using it. The Code completion isn’t upto my liking yet, but it is helpful at times.

Using Standard Python Libraries

Since my original code was written on linux, it used only the standard python modules. In a manner of speaking, it was “pure” python code. Since IronPython is an implementation of the Python programming language running under .NET, it was obivious that my code may not work as is. But I’m glad that I did not have to make too many changes to get it working under IronPython.

As is well documented in IronPython Tutorial, it is not very difficult to use standard python libraries with IronPython (with a few exceptions – more about this a little later) To get IronPython to use Standard Python Modules,  one needs to add the following two lines to C:\IronPython-2.0.1\Lib\site.py :

import sys
sys.path.append(r"C:\Python25\Lib")

While this works for most part, it doesn’t help if you are using Python extensions written in C. More about my specific problems in another post. But there is an open source project IronClad to deal specifically with this issue. In the meantime, you can check the differences between IronPython and CPython

Related articles

• IronPython in Action (blogs.msdn.com)
• Why Python? (mehmetalierturk.com)

Debugging Python Scripts

Found a great way to debug python scripts interactively using pdb aka Python Debugger. It is similar to gdb used on *nix.
Essentially you import pdb in the beginning of the script, and wherever you need to start debugging, add following statement :
pdb.set_trace()
Now you execute the script from command line, and execution will stop where you have added set_trace() call. You are presented with pdb prompt. There after it is similar to gdb commands.

Read more..

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