root[:]=[root,root]

[Terry Reedy]

On 12/16/2011 9:40 PM, YAN HUA wrote:
> Hi,all. Could anybody tell how this code works?
>  >>> root = [None, None]
>  >>> root[:] = [root, root]
>  >>> root
> [[...], [...]]
>  >>> root[0]
> [[...], [...]]
>  >>> root[0][0][1][1][0][0][0][1][1]
> [[...], [...]]

A simpler example:
 >>> l = []
 >>> l.append(l)
 >>> l
[[...]]

Python is (now) smart enough to recognize a recursive list and print 
'...' instead of going into an infinite loop printing '['s (as it once 
did, I believe).

-- 
Terry Jan Reedy