On 2014-02-18 14:11, MRAB wrote:
On 2014-02-18 13:48, Serhiy Storchaka wrote:
18.02.14 10:10, Paul Moore написав(ла):
Or alternatively, a "default on None" function - Oracle SQL calls this
nvl, so I will too:
def nvl(x, dflt):
return dflt if x is None else x
results = sorted(invoices, key=lambda x: nvl(x.duedate, datetime(MINYEAR,1,1))
Or, as was proposed above:
results = sorted(invoices,
key=lambda x: (x.duedate is not None, x.duedate))
That makes me wonder.
Why is:
None < None
unorderable and not False but:
(None, ) < (None, )
orderable?
tuple's rich comparison uses PyObject_RichCompareBool(x, y, Py_EQ) to find the
first pair of items that is unequal. Then it will test the order of any
remaining elements.
http://hg.python.org/cpython/file/79e5bb0d9b8e/Objects/tupleobject.c#l591
PyObject_RichCompareBool(x, y, Py_EQ) treats identical objects as equal.
http://hg.python.org/cpython/file/79e5bb0d9b8e/Objects/object.c#l716
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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