py3: replace None with -1 to sort an integer array...
py3: replace None with -1 to sort an integer array
In Python 2:
>>> ls = [4, 2, None]
>>> sorted(ls)
[None, 2, 4]
In Python 3:
>>> ls = [4, 2, None]
>>> sorted(ls)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unorderable types: NoneType() < int()
Therefore we replaced None with -1, and the safe part is that, None and -1 are
only the keys which are used for sorting so we don't need to convert the -1's
back to None.