Mercurial > cpython-lru_cache-weakref
diff Python/bltinmodule.c @ 56751:7dc57b991d83
Merged revisions 75714 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r75714 | mark.dickinson | 2009-10-26 14:18:44 +0000 (Mon, 26 Oct 2009) | 1 line
Warn against replacing PyNumber_Add with PyNumber_InPlaceAdd in sum
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| author | Mark Dickinson <dickinsm@gmail.com> |
|---|---|
| date | Mon, 26 Oct 2009 14:19:42 +0000 |
| parents | 0f9e8d3ecac3 |
| children | 087fe5fa113c |
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--- a/Python/bltinmodule.c Mon Oct 26 12:01:06 2009 +0000 +++ b/Python/bltinmodule.c Mon Oct 26 14:19:42 2009 +0000 @@ -1958,6 +1958,15 @@ } break; } + /* It's tempting to use PyNumber_InPlaceAdd instead of + PyNumber_Add here, to avoid quadratic running time + when doing 'sum(list_of_lists, [])'. However, this + would produce a change in behaviour: a snippet like + + empty = [] + sum([[x] for x in range(10)], empty) + + would change the value of empty. */ temp = PyNumber_Add(result, item); Py_DECREF(result); Py_DECREF(item);