一方面,人们很容易看到关键功能,可以很容易地采用一种使用比较功能的同类功能。 减少如下:
def compare(x,y):
return key(x) - key(y)
另一方面,我们如何知道,我们如何通过使用钥匙的地图限制各种类型的要素,确保我们不会失去潜在的分类? 例如,如果我坚持以下比较方法,那么我就想确定一个长2个 t子(x,y)的清单:
def compare(tup1,tup2):
if (tup1[1] < tup2[0]):
return -1
if (tup1[0] % 2 == 0):
return 1
if (tup1[0] - tup2[1] < 4):
return 0
else:
return 1
现在我要告诉我,我如何将这一比较转化为相应的“关键”职能,这样,我的分类算法就以同样的方式行事? 这不是一个有争议的例子,因为这些类型的定制分类显示在搜索过程中的计量分解算法,而且非常重要。
functools.cmp_to_key,这将保障与你的比较功能相同的分类行为。 这一职能的来源见:http://wiki.python.org/moin/HowTo/Sorting#The_Old_Way_Using_the_cmp_Para下。 Sorting How To document。
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