[EMAIL PROTECTED] wrote: > I am puzzled by the failure on 'a in a' for a=[a]. >>> a== [a] also > fails. Can we assume/surmise/deduce/infer it's intentional? > It may be less confusing if instead of an assignment following by a test you just consider doing the test at the same time as the assignment (then again it changes the behaviour so it may just be more confusing).
There is a very limited set of values for which you would expect this output: >>> a==[a] True >>> a in [a] True The most obvious one is a simple recursive list: >>> a = [] >>> a.append(a) >>> a==[a]; a in [a] True True Pushing the recursion down a level breaks some of the comparisons: >>> a = [[]] >>> a[0].append(a) >>> a==[a] Traceback (most recent call last): File "<stdin>", line 1, in <module> RuntimeError: maximum recursion depth exceeded in cmp >>> a in [a] True >>> a in a Traceback (most recent call last): File "<stdin>", line 1, in <module> RuntimeError: maximum recursion depth exceeded in cmp which may be considered a bug or possibly it is just a limit of the implementation. This also produces an overflow (in fact I think it is just the same situation as above, recursing on the same list is handled, recursing on different but equivalent lists is not): >>> a = []; a.append(a) >>> b = []; b.append(b) >>> a==b Traceback (most recent call last): File "<stdin>", line 1, in <module> RuntimeError: maximum recursion depth exceeded in cmp -- http://mail.python.org/mailman/listinfo/python-list
