Python-查找值大于零的最高字典键

Question

我有一本字典

{0: 12, 1: 1, 2: 13, 3: 7, 4: 0}

我想找到值大于0的最高字典键。

在本例中，答案是 3。

最好的方法是什么？

Answer 1

使用geneexpr过滤掉“坏”值，并使用max保留剩余的最高值:

# On Py2, use .iteritems() instead of .items()
max(k for k, v in mydict.items() if v > 0)

或者，如果没有键符合条件而没有引发异常，则如果您需要默认值:

# Py3 max has default, which makes this super-easy:
max((k for k, v in mydict.items() if v > 0), default=SOMEVALUEGOESHERE)

# Py2 doesn't have default; workaround is to catch exception and use a default (EAFP):
try:
    mymax = max(k for k, v in mydict.iteritems() if v > 0)
except ValueError:
    mymax = SOMEVALUEGOESHERE

# Or if you can't do that for some reason, make a listcomp instead of genexpr
# and check for at least one surviving key before calling max (LBYL)
goodkeys = [k for k, v in mydict.iteritems() if v > 0]
mymax = max(goodkeys) if goodkeys else SOMEVALUEGOESHERE