[Python-ideas] max() allowed to take empty list

[Tom Pinckney]

Many functions are happy to take empty lists:

>>> map(lambda x: x, [])
[]
>>> filter(lambda x: x == 1, [])
[]
>>> sum(a)
0
>>> reduce(lambda x,y: x+y, [], 0)
0

But not max():

>>> max([])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: max() arg is an empty sequence

Allowing max to return None would make a lot of functional style programming easier, instead of explicitly having to check for empty lists or ignoring exceptions.

None makes sense as a return value in many contexts. For example, hypothetical code like:

if max(values) >= 90: return True   # works even if values is []

thought not every case:

a / max(values)   # can't divide by None if values is []