py3: more trivial fixes to sage.rings.polynomial.polydict

[tscrim]

LGTM.

[vbraun]

File "src/sage/rings/polynomial/polydict.pyx", line 982, in sage.rings.polynomial.polydict.ETuple.__init__
Failed example:
    ETuple(iter([2, 3, 4]))
Expected:
    Traceback (most recent call last):
    ...
    TypeError: Error in ETuple((), <list... object at ...>, None)
Got:
    <BLANKLINE>
    Traceback (most recent call last):
      File "/home/sage-patchbot/sage/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 650, in _run
        self.compile_and_execute(example, compiler, test.globs)
      File "/home/sage-patchbot/sage/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 1061, in compile_and_execute
        exec(compiled, globs)
      File "<doctest sage.rings.polynomial.polydict.ETuple.__init__[3]>", line 1, in <module>
        ETuple(iter([Integer(2), Integer(3), Integer(4)]))
      File "sage/rings/polynomial/polydict.pyx", line 1007, in sage.rings.polynomial.polydict.ETuple.__init__ (build/cythonized/sage/rings/polynomial/polydict.c:13297)
        self._length = len(data)
    TypeError: object of type 'listiterator' has no len()

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​4d7aa64

py3: fix this example to ensure it works consistently on python 2 and 3

[embray]

It seems Cython on Python 2 has some strange behaviors if you put isinstance(..., range). So I'm just going to drop that change until we have a better, consistent way to accept arbitrary sequence types in function arguments.

[tscrim]

Replying to embray:

It seems Cython on Python 2 has some strange behaviors if you put isinstance(..., range). So I'm just going to drop that change until we have a better, consistent way to accept arbitrary sequence types in function arguments.

I would guess that comes from the fact that range on Cython is treated as special by the compiler as it can both be treated as xrange (e.g., in a for loop) and as a list:

sage: %%cython
....: def test(n):
....:     return range(n)
sage: test(5)
[0, 1, 2, 3, 4]

[embray]

Well, yes, but I'm not sure how it translates a statement like isinstance(..., range) and I didn't bother to look, but it seems to get up to some funny business for sure.