Standard Deviation One-liner

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From	Billy Mays <noway@nohow.com>
Newsgroups	comp.lang.python
Subject	Standard Deviation One-liner
Date	Fri, 03 Jun 2011 13:55:02 -0400
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I'm trying to shorten a one-liner I have for calculating the standard 
deviation of a list of numbers.  I have something so far, but I was 
wondering if it could be made any shorter (without imports).


Here's my function:

a=lambda d:(sum((x-1.*sum(d)/len(d))**2 for x in d)/(1.*(len(d)-1)))**.5


The functions is invoked as follows:

 >>> a([1,2,3,4])
1.2909944487358056

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Standard Deviation One-liner Billy Mays <noway@nohow.com> - 2011-06-03 13:55 -0400
  Re: Standard Deviation One-liner Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2011-06-03 20:50 +0200
    Re: Standard Deviation One-liner Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2011-06-03 21:10 +0200
  Re: Standard Deviation One-liner Raymond Hettinger <python@rcn.com> - 2011-06-03 13:09 -0700
    Re: Standard Deviation One-liner Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-06-05 17:26 +0000
      Re: Standard Deviation One-liner Ethan Furman <ethan@stoneleaf.us> - 2011-06-05 12:17 -0700

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