[Python-Dev] [Python-checkins] cpython (3.3): Issue #16045: add more unit tests for built-in int()

[Chris Jerdonek]

On Sun, Dec 23, 2012 at 6:19 PM, Terry Reedy <tjreedy at udel.edu> wrote:
> On 12/23/2012 4:47 PM, Chris Jerdonek wrote:
>> On Sun, Dec 23, 2012 at 12:03 PM, Terry Reedy <tjreedy at udel.edu> wrote:
>>>
>>>> +    # For example, PyPy 1.9.0 raised TypeError for these cases because
>>>> it
>>>> +    # expects x to be a string if base is given.
>>>> +    @support.cpython_only
>>>> +    def test_base_arg_with_no_x_arg(self):
>>>> +        self.assertEquals(int(base=6), 0)
>>>> +        # Even invalid bases don't raise an exception.
>>>> +        self.assertEquals(int(base=1), 0)
>>>> +        self.assertEquals(int(base=1000), 0)
>>>> +        self.assertEquals(int(base='foo'), 0)
>>>
>>> I think the above behavior is buggy and should be changed rather than
>>> frozen
>>> into CPython with a test. According to the docs, PyPy does it right.
>
> In any case, the discrepancy between doc and behavior is a bug and should be
> fixed one way or the other way. Unlike int(), I do not see a realistic use
> case for int(base=x) that would make it anything other than a bug.

Just to be clear, I agree with you that something needs fixing (and
again, I did not commit the patch).  But I want to clarify a couple of
your responses to my points.


>> One way to partially explain CPython's behavior is that when base is
>> provided, the function behaves as if x defaults to '0' rather than 0.
>
>
> That explanation does not work. int('0', base = invalid) and int(x='0',
> base=invalid) raise TypeError or ValueError.

I was referring to the behavioral discrepancy between CPython
returning 0 for int(base=valid) and the part of the docstring you
quoted which says, "It is an error to supply a base when converting a
non-string."  I wasn't justifying the case of int(base=invalid).
That's why I said "partially" explains.  The int(base=valid) case is
covered by the following line of the CPython-specific test that was
committed (which in PyPy raises TypeError):

+        self.assertEquals(int(base=6), 0)

> If providing a value explicit
> changes behavior, then that value is not the default. To make '0' really be
> the base-present default, the doc and above behavior should be changed. Or,
> make '' the default and have int('', base=whatever) return 0 instead of
> raising. (This would be the actual parallel to the str case.)


>> This is similar to the behavior of str(), which defaults to b'' when
>> encoding or errors is provided, but otherwise defaults to '':
>
> This is different. Providing b'' explicitly has no effect.
> str(encoding=x, errors=y) and str(b'', encoding=x, errors=y) act the same.
> If x or y is not a string, both raise TypeError. (Unlike int and base.) A
> bad encoding string is ignored because the encoding lookup is not done
> unless there is something to encode. (This is why the ignore-base
> base-default should be '', not '0'.) A bad error specification is (I
> believe) ignored for any error-free bytes/encoding pair because, again, the
> lookup is only done when needed.

Again, I was referring to the "valid" case.  My point was that str()'s
object argument defaults to '' when encoding or errors isn't given,
and otherwise defaults to b''.  You can see that the object argument
defaults to '' in the simpler case here:

>>> str(), str(object=''), str(object=b'')
('', '', "b''")

But when the encoding argument is given the default is different (it is b''):

>>> str(object='', encoding='utf-8')
TypeError: decoding str is not supported
>>> str(encoding='utf-8'), str(object=b'', encoding='utf-8')
('', '')

But again, these are clarifications of my comments.  I'm not
disagreeing with your larger point.

--Chris