Re: root[:]=[root,root]

From	Terry Reedy <tjreedy@udel.edu>
Subject	Re: root[:]=[root,root]
Date	2011-12-17 22:08 -0500
References	<CAPoCtLbKBqU3qkGUmOR7jF3tZogQZUZbOWnAgYBtP3qkAQ5+Bw@mail.gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.3776.1324177728.27778.python-list@python.org> (permalink)

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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

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Re: root[:]=[root,root] Terry Reedy <tjreedy@udel.edu> - 2011-12-17 22:08 -0500

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