Rotating lists?

Thorsten Kampe thorsten at thorstenkampe.de
Thu Sep 16 09:09:57 CEST 2004


* Ivan Voras (2004-09-16 00:10 +0200)
> I need to transform this:
> 
> [1,2,3]
> 
> into this:
> 
> [2,3,1]
> 
> (a left-rotation. Actually, any rotation will do).
> 
> I tried:
> 
> a = a[1:] + a[0]
> 
> which doesn't work because there's no __add__ between a list and 
> integer, and:
> 
> a = a[1:].append(a[0])
> 
> but it doesn't work, since append returns None :( Right now, I'm doing 
> it with a temporary variable and it looks ugly - is there an elegant way 
> of doing it?

def rotate(seq,
           offset):
    """ shift seq to the left by offset, with the elements shifted off the
    beginning inserted back at the end """
    return seq[offset:] + seq[:offset]



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