Newbie questions for Python usage

[Caolan]

Hello,
 
I am fairly new to Python and after exploring the language some I have some questions:
 

1.	I understand HOW to use the lambda operator, but WHY would you want to use it? Can anyone please give an example of WHY you would need it as opposed to just declaring a function either in the local scope, or outside? 
2.	I would like to be able to declare as a member attribute a file object, however because there is no declaration of variable types like there is in C++, there doesn't seem to be a way to do this without first making a fobj = open(...) call. Is this true?
3.	Now for an os import question for Windows. I wish to automate the builds of VS.NET 2005 and I can do so by executing the os.system(...) command however I cannot see how to execute the vcvars32.cmd first to set environment variables and then execute the actual command-line for the build itself.

Thanks for the help all!

Caolan

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