Question

如果我有一个列表和一个计算分数的函数，我可以计算argmax：

maxscore = 0; argmax = None
x = [3.49, 0.122, 293, 0.98] # Imagine a LARGE list.
for i in x:
    # Maybe there're some other func() to calculate score
    # For now just sum the digits in i.
    score = sum([int(j) for j in str(i) if j.isdigit()])
    print i, score
    if maxscore < score:
        maxscore = score
        argmax = i

还有其他方法可以实现argmax吗？什么是pythonic方式呢？

Answer 1

def score(i):
    return sum([int(j) for j in str(i) if j.isdigit()])

max(x, key=score)

Answer 2

如果您要为大型非Unicode字符串列表做很多事情，那么设置的一次性开销可能是值得的，因为尽可能多的过程可以通过相对简单的表来完成-lookups和用C编写的内置方法（如string_translate()在CPython中）：

x = [3.49, 0.122, 293, 0.98]

digits = set(range(ord('0'), ord('9')+1))
transtable = ''.join(chr(i-ord('0')) if i in digits else chr(0)
                        for i in range(256))
deletechars = ''.join(chr(i) for i in range(256) if i not in digits)

def sum_digit_chars(i):
    return sum(bytearray(str(i).translate(transtable, deletechars)))

print max(x, key=sum_digit_chars)

什么是计算argmax的pythonic方法？

2 个答案: