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, [...]]
>>>

The ... denotes a recursive data structure, which is what you've created here by "a" including itself as an element. I'm not clear what you expected to see, but I'm going to close this because I don't see an actual problem here. If you think there's a bug in Python, please describe it here. Also make sure to include what you expect to see in addition to what you do see.

Lingaraj: the fact that you use IDLE to run Python code, with the same binary executable that is running IDLE, does not make the result an IDLE issue.  (This is a common mistake of beginners who use IDLE.)

Anyway, an infinite string, the 'accurate' result, or an out-of-memory or recursion-depth exception, the original result of trying to print recursive data objects, is even less practical ;-).  This fix, a compact replacement, is intentional.