I'm about to undertake a .NET project: We need to create a create a program that utilize some existing C# code, and I'm hoping to use IronPython. (I'm an experienced Python programmer, but a bit of a .NET newbie). 
My question is: Is IronPython a good fit for using mostly C# code, or would it be better just to use C#? If IronPython is a good fit, are there any pitfalls to look out for?
You'll need to compile the C# code into an assembly (DLL) you can use within IronPython.  Once you do this, IronPython can use this just like any other .NET assembly.
This is a common usage scenario for IronPython.
Using C# code in IronPython