我如何测试以查看Python中的defaultdict(set)是否为空

Question

我有一个defaultdict fishparts = defaultdict(set),它有分配给它的元素但是定期清除使用.clear()我需要的东西是某种方式来测试集合是否清除所以我可以在下面的函数中做一些其他的工作.

def bandpassUniqReset5(player,x,epochtime):
    score = 0
    if lastplay[player] < (epochtime - 300):
        fishparts[player].clear()
    lastplay[player] = epochtime
    for e in x:
        # right here I want to do a check to see if the "if" conditional above has cleared fishparts[player] before I do the part below
        if e not in fishparts[player]:
            score += 1
        fishparts[player].add(e)
    return str(score)

Answer 1

与所有Python容器一样,集合在空时被视为False:

if not fishparts[player]:
    # this set is empty

请参阅真值测试.

演示:

>>> if not set(): print "I am empty"
... 
I am empty
>>> if set([1]): print "I am not empty"
... 
I am not empty