New submission from Maytag Metalark:
`None` should never be the result of the built-in `min` and `max` functions.
When `None` is supplied as one of the values to check, it should never be
chosen as the result.
This would make it much easier to find a minimum and/or maximum while iterating
over values. For instance, the following is a common pattern:
mn = None
mx = None
for x in iterable:
if mn is None or x < mn:
mn = x
if mx is None or x > mx:
mx = x
Note that although the `min` and `max` functions could be applied directly to
`iterable` in the above case, the above pattern is more efficient (only once
through the loop) and covers the common case where additional operations are
performed on each value of the iterable.
If the suggested enhancement was made, the above code could be written more
simply as:
mn = None
mx = None
for x in iterable:
mn = min(mn, x)
mx = max(mx, x)
At present, this will actually work for `max`, as None evaluates as less than
every number, but it will not work for `min` (for the same reason).
The suggested change would mean that None is simultaneously greater than and
less than every other value, but that only matters if we assume a total
ordering of all the values including None, which doesn't seem like it would be
important.
----------
messages: 231998
nosy: Brian.Mearns
priority: normal
severity: normal
status: open
title: Use of None in min and max
type: enhancement
versions: Python 2.7
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22979>
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