... but here at PDW we abhor that kind of defeatism!
>>> import ctypes
>>> tup = (None,)
>>> ctypes.pythonapi.PyTuple_SetItem.argtypes = ctypes.c_void_p, ctypes.c_int, ctypes.c_void_p
>>> ctypes.pythonapi.PyTuple_SetItem(id(tup), 0, id(tup))
0
Showing the tuple itself is a little problematic
>>> tup
# ... hundreds of lines of parens ...
(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
(((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((
((Segmentation fault
This is not surprising, since C-API is actually used. Without it, making a tuple instance with a part of itself will not possible.
ReplyDeleteyup! only the C-API makes it possible
Deleteit is kind of interesting though that tuple doesn't have any recursion handling in its repr()
>>> a = []
>>> a.append((a,))
>>> a
[([...],)]
>>> a[0]
([([...],)],)
rather than tuple(list(tuple)) showing ([(...,)]) it relies on the list repr() to detect the cycle and handle it one layer deeper
contract with dict(list(dict)) in which the dict repr() detects the cycle
>>> b = {}
>>> b[0] = [b]
>>> b
{0: [{...}]}
Odd; not getting this error under ipython, though I do get it with plain python. Both should(?) be running the same python executable; at any rate both report running 2.7.15 (can't even try this in python3 it seems). But under ipython I just get ((...),) as one might expect.
ReplyDeleteI have bookmarked your blog, the articles are way better than other similar blogs.. thanks for a great blog! 统计代写
ReplyDelete