Re: [Python-ideas] Add irange with large integer step support to itertools

-1 for any proposal that adds anything differentiating int/long. -Zac On Mon, Jan 10, 2011 at 7:52 PM, Nick Coghlan wrote:

On Mon, Jan 10, 2011 at 6:27 PM, Mark Dickinson wrote:

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Python 3.1.3 (r313:86834, Nov 28 2010, 10:01:07) [GCC 4.4.5] on linux2 Type "help", "copyright", "credits" or "license" for more information.

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range(10**10000, 10**10000+10**1000, 10**900)[5] Traceback (most recent call last): File "<stdin>", line 1, in <module> OverflowError: Python int too large to convert to C ssize_t

Note that the problem isn't actually the step value - it's the overall length of the resulting sequence.

If you make the sequence shorter, it works (at least in 3.2, I didn't check earlier versions):

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x = range(10**10000, 10**10000+(500*10**900), 10**900) len(x) 500 x[5] <snip really big number>

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This example strikes me as a bug in range (specifically, in range_subscript in Objects/rangeobject.c).

The main issue is actually in range_item rather than range_subscript - we invoke range_len() there to simplify the bounds checking logic. To remove this limitation, the C arithmetic and comparison operations in that function need to be replaced with their PyLong equivalent, similar to what has been done for compute_range_length().

There's a related bug where range_subscript doesn't support *indices* greater than sys.maxsize - given an indexing helper function that can handle a range length that doesn't fit in sys.maxsize, it would be easy to call that unconditionally rather than indirectly via range_item, fixing that problem as well.

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Does such an addition make sense in your eyes?

Wouldn't it be better to fix 'range' to behave as expected?

Agreed. It isn't a deliberate design limitation - it's just a consequence of the fact that converting from C integer programming to PyLong programming is a PITA, so it has been a process of progressive upgrades in range's support for values that don't fit in sys.maxsize.

Cheers, Nick.

-- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas