python：使用迭代器模块进行多对多分组

发布于 2024-11-06 19:15:38 字数 446 浏览 0 评论 0原文

我有一个可迭代的项目，其中的项目映射到多个组。如何使用迭代器模块对项目进行分组？

animals = (human, frog, giraffe, fish)

这里人、青蛙等是具有属性的对象：is_land_dwelling和is_water_dwelling。

我想根据这些属性对动物进行分组，

groupings = dwelling_classifier(animals)

应该返回一些组迭代器，该迭代器将动物分成几部分，

is_land_dwelling: human, frog, giraffe
is_water_dwelling: frog, fish

我宁愿只对可迭代对象进行一次传递。那么，除了编写我的自定义迭代器函数之外，还有其他方法吗？

原文

I have an iterable, items of which map to multiple groups. How do I group the items using an iterator module?

animals = (human, frog, giraffe, fish)

Here human, frog, etc are objects with attributes: is_land_dwelling and is_water_dwelling.

I want to group animals based on these attributes

groupings = dwelling_classifier(animals)

should return some group iterator which splits animals into

is_land_dwelling: human, frog, giraffe
is_water_dwelling: frog, fish

I would prefer to make only single pass over the iterable. So, apart from writing my custom iterator function, is there any other way?

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玩世 2024-11-13 19:15:38

def is_water_dwelling(animal):
    return animal in ('frog', 'fish')


def is_land_dwelling(animal):
    return animal in ('frog', 'human', 'giraffe')

animals = ('human', 'frog', 'fish', 'giraffe')

land_dwelling = (x for x in animals if is_land_dwelling(x))
water_dwelling = (x for x in animals if is_water_dwelling(x))

print list(land_dwelling)
print list(water_dwelling)

请注意，land_dwelling 和 water_dwelling 是生成器。

通过将相关分类函数保存在某种字典中（可能由分类类型键入），可以将其推广到任意数量的“分类器”。像这样的东西（未测试）：

kinds = {'water': is_water_dwelling, 'land': is_land_dwelling, 'air': is_flying}
result = {}

for kind, classifier in kinds.iteritems():
  result[kind] = [x for x in animals if classifier(x)]

# If you just want to go over animals once, you can do this instead:
from collections import defaultdict
result = defaultdict(list)

for x in animals:
  for kind, classifier in kinds.iteritems():
    if classifier(x):
      result[kind].append(x)

def is_water_dwelling(animal):
    return animal in ('frog', 'fish')


def is_land_dwelling(animal):
    return animal in ('frog', 'human', 'giraffe')

animals = ('human', 'frog', 'fish', 'giraffe')

land_dwelling = (x for x in animals if is_land_dwelling(x))
water_dwelling = (x for x in animals if is_water_dwelling(x))

print list(land_dwelling)
print list(water_dwelling)

Note that land_dwelling and water_dwelling are generators.

This can be generalized for any amount of "classifiers", by holding the relevant classification functions in a dictionary of some kind, possibly keyed by classification type. Something like this (not tested):

kinds = {'water': is_water_dwelling, 'land': is_land_dwelling, 'air': is_flying}
result = {}

for kind, classifier in kinds.iteritems():
  result[kind] = [x for x in animals if classifier(x)]

# If you just want to go over animals once, you can do this instead:
from collections import defaultdict
result = defaultdict(list)

for x in animals:
  for kind, classifier in kinds.iteritems():
    if classifier(x):
      result[kind].append(x)

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