| msg168439 - (view) |
Author: Rostyslav Dzinko (Rostyslav.Dzinko) |
Date: 2012-08-17 11:17 |
| I've encountered that OverflowError which can happen in __len__ method is still undocumented, though one issue on this problem: http://bugs.python.org/issue12159 ended up with "need to be documented" comment. Link to documentation: http://docs.python.org/reference/datamodel.html#object.__len__ I think it must be clarified that __len__ return value is constrained to upper boundary (Py_ssize_t c type) when you plan to call it via len() built-in function. |
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| msg168473 - (view) |
Author: Terry J. Reedy (terry.reedy) *  |
Date: 2012-08-17 20:18 |
| In #12159, Victor correctly labelled this an implementation (IE, CPython) detail (limitation). I don't believe any implementation has to limit the range of len(). So the question is whether we should add a CPython implementation limit note, including the possibility of OverflowError, and if so, to both len() and __len__() entries. I am not sure of the current doc policy. The second sentence of the len entry is out of date. " The argument may be a sequence (string, tuple or list) or a mapping (dictionary)." Sets and any collections with a size (__len__ method) can also be arguments. I am not sure how to revise that either. |
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| msg257312 - (view) |
Author: Camilla Montonen (Winterflower) |
Date: 2016-01-01 22:31 |
| The deficiency noticed by Terry has been at least partially corrected in the len() docs https://docs.python.org/2/library/functions.html#len Return the length (the number of items) of an object. The argument may be a sequence (such as a string, bytes, tuple, list, or range) or a collection (such as a dictionary, set, or frozen set). It doesn't mention the fact that the collection has to implement __len__, but I suppose that might be obvious to experienced Python users (isn't obvious to a beginner like me, though). So perhaps this might be a welcome clarification. The issue regarding OverflowError raised by Rostyslav still remains unresolved. |
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| msg257318 - (view) |
Author: Martin Panter (martin.panter) * |
Date: 2016-01-01 23:47 |
| Issue 10289 proposes to link from len() to __len__() in the documentation. I think the limitation only needs to be documented for __len__(); there are other ways to invoke it as well. |
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| msg292123 - (view) |
Author: Terry J. Reedy (terry.reedy) * |
Date: 2017-04-22 16:09 |
| Has or will builtin classes be modified to follow advice to include a separate __bool__? In 3.6.1, >>> r = range(19**100) >>> bool(r) Traceback (most recent call last): File "<pyshell#1>", line 1, in bool(r) OverflowError: Python int too large to convert to C ssize_t |
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| msg292125 - (view) |
Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2017-04-22 16:28 |
| Yes, and the range object already is fixed by . |
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| msg292151 - (view) |
Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2017-04-23 05:38 |
| New changeset 85157cd89a6edac347a5b6871fcf20c500c6fbbf by Serhiy Storchaka in branch 'master': bpo-15718: Document the upper bound constrain on the __len__ return value. (#1256) https://github.com/python/cpython/commit/85157cd89a6edac347a5b6871fcf20c500c6fbbf |
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| msg292152 - (view) |
Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2017-04-23 05:50 |
| New changeset f2ed2858eea7569c8915b3611ca5ec92ae10b17f by Serhiy Storchaka in branch '3.6': [3.6] bpo-15718: Document the upper bound constrain on the __len__ return value. (GH-1256) (#1259) https://github.com/python/cpython/commit/f2ed2858eea7569c8915b3611ca5ec92ae10b17f |
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| msg292153 - (view) |
Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2017-04-23 05:50 |
| New changeset c358536fd5e40e8f29ee4f086588a82fccb25a09 by Serhiy Storchaka in branch '3.5': [3.5] bpo-15718: Document the upper bound constrain on the __len__ return value. (GH-1256) (#1260) https://github.com/python/cpython/commit/c358536fd5e40e8f29ee4f086588a82fccb25a09 |
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| msg292154 - (view) |
Author: Serhiy Storchaka (serhiy.storchaka) * |
Date: 2017-04-23 05:58 |
| New changeset bfc7dff63b9b30371e3423a5c35ccda2f3b52218 by Serhiy Storchaka in branch '2.7': [2.7] bpo-15718: Document the upper bound constrain on the __len__ return value. (GH-1256). (#1261) https://github.com/python/cpython/commit/bfc7dff63b9b30371e3423a5c35ccda2f3b52218 |
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