[Python-Dev] PyPy progress: list of CPython 3.5 crashers and bugs (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Tue Dec 6 01🔞45 EST 2016

On 05.12.16 20:38, Terry Reedy wrote:

I believe that this item in your list is a design choice rather than a bug. "* collectionsmodule.c: dequerepr uses "[...]" as repr if recursion is detected. I'd suggest that "deque(...)" is clearer---it's not a list."

I strongly suspect that Raymond H. intentionally choose to consistently represent deques as "deque()" With recursion, some current results are:

import collections as c d = c.deque() d.append(d) d deque([[...]]) d.append(1) d deque([[...], 1]) d.rotate() d deque([1, [...]]) l = [] l.append(l) d2 = c.deque(l) d2 deque([[[...]]]) With ... now being valid, all of these evaluate to a finite structure with a different representation ('Ellipsis' replacing '...'). The same would be true of what I believe is your proposal for the first example above: "deque(deque(...))". I can see why you might prefer it. On the other hand, it could be seen as falsely implying that the object is the result two calls to deque. In any case, changing the repr (and possibly breaking existing code) would be an enhancement issue for 3.7 at the earliest. At least it is the case that the representation of a pure recursive deque and a deque containing a pure recursive list are different.

There was a discussion about this a year ago. I proposed to use <...> or <deque object at ...> for disambiguation.

https://mail.python.org/pipermail/python-ideas/2015-December/037537.html https://mail.python.org/pipermail/python-ideas/2015-December/037544.html

More information about the Python-Dev mailing list