Currently the output of below append cannot be used for practical purpose, This jira is to get the expectation for a case in append.
>>> a=[1,2]
>>> a.append(a)
>>> a
[1, 2, [...]]
>>>
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4What are you expecting to happen here, and what is wrong with what you get? – Daniel Roseman Dec 05 '18 at 19:41
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It's not clear what you're asking for. Are you just trying to get the list "`[1,2,1,2]`" instead of the nested list "`[1, 2, [1,2] ]`"? If so, a simple `a+a` will do it. – Bill M. Dec 05 '18 at 19:44
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@DanielRoseman thanks for the response, is there any Python documentation which explains this behaviour ? I understood the reason but I was expecting it to be [1,2,[1,2]] – Lingaraj Gowdar Dec 05 '18 at 20:45
2 Answers
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The third element is the entire list (i.e. a[2] is a, or id(a[2]) == id(a)). Because a contains itself, printing it would go on infinitely (a[2][2][2][2][2]...[2] == a), so the string conversion just gives you the "[...]" output.
manveti
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I did not know Python allowed a recursive list, nor that it had a special syntax for displaying it. – Mark Ransom Dec 05 '18 at 19:47
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1@MarkRansom it's not so much a recursive list as it is an eternal self-referential loop... – wpercy Dec 05 '18 at 19:51
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The answer by Craig Meier explains why you're getting the output you're seeing. To eliminate the problem, make a copy of the list when you append it. A slice is the easiest way of copying a list.
>>> a=[1,2]
>>> a.append(a[:])
>>> a
[1, 2, [1, 2]]
Mark Ransom
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