Python：元组/字典作为键，选择，排序 [英] Python: Tuples/dictionaries as keys, select, sort

问题描述

假设我有不同颜色的水果，例如24个蓝色香蕉，12个绿色苹果，0个蓝色草莓等。
我想在Python中的一个数据结构中组织它们，可以方便地进行选择和排序。我的想法是把它们放入一个字典中，以元组作为键，例如

  {（'banana'，'blue'） ：24，
（'apple'，'green'）：12，
（'strawberry'，'blue'）：0，
 ... 
} 
  

甚至是字典，例如

 ：$ {$'$'$'$'''''''' ，
 {'fruit'：'strawberry'，'color'：'blue'}：0，
 ... 
} 
  pre> 
 
 
我想要检索所有蓝色水果或所有颜色的香蕉的列表，或者按照水果的名称对该字典进行排序。有没有办法以干净的方式这样做？
 
 
 
很可能，使用元组作为键的字典不是正确的方式来处理这种情况。
 
 
 
所有建议欢迎！
解决方案
我喜欢python的东西是元组合的组合。你在这里实际上是一个2d数组（其中x =水果名称和y =颜色），我一般是支持实现二维数组的元组的dict，至少当像 numpy 或数据库不太合适。所以简而言之，我认为你有一个很好的方法。
 
 
 
请注意，你不能在dict中使用diction作为key，而不需要做一些额外的工作，所以不是很好的解决方案。 
 
 
 
也就是说，你也应该考虑 namedtuple（）。这样你可以这样做：
 >>>从集合导入namedtuple 
>>> Fruit = namedtuple（Fruit，[name，color]）
>>> f = Fruit（name =banana，color =red）
>>>打印f 
水果（name ='banana'，color ='red'）
>>> f.name 
'banana'
>>> f.color 
'red'
  
现在你可以使用你的fruitcount dict：
 >>> fruitcount = {Fruit（banana，red）：5} 
>>> fruitcount [f] 
 5 
  
其他技巧：
 >>> fruits = fruitcount.keys（）
>>> fruits.sort（）
>>>打印水果
 [Fruit（name ='apple'，color ='green'），
 Fruit（name ='apple'，color ='red'），
 Fruit（name = Fruit'，color ='blue'），
 Fruit（name ='strawberry'，color ='blue'）] 
>>> fruits.sort（key = lambda x：x.color）
>>>>打印水果
 [Fruit（name ='banana'，color ='blue'），
 Fruit（name ='strawberry'，color ='blue'），
 Fruit（name =苹果'，color ='green'），
 Fruit（name ='apple'，color ='red'）] 
  
回应chmullig，要获得一个水果的所有颜色的列表，您必须过滤键，即
 code> bananas = [水果果实果实如果fruit.name =='banana'] 
  
 
suppose I have quantities of fruits of different colors, e.g., 24 blue bananas, 12 green apples, 0 blue strawberries and so on.
I'd like to organize them in a data structure in Python that allows for easy selection and sorting. My idea was to put them into a dictionary with tuples as keys, e.g.,
{ ('banana',    'blue' ): 24,
  ('apple',     'green'): 12,
  ('strawberry','blue' ): 0,
  ...
}
or even dictionaries, e.g.,
{ {'fruit': 'banana',    'color': 'blue' }: 24,
  {'fruit': 'apple',     'color': 'green'}: 12,
  {'fruit': 'strawberry','color': 'blue' }: 0,
  ...
}
I'd like to retrieve a list of all blue fruit, or bananas of all colors, for example, or to sort this dictionary by the name of the fruit. Are there ways to do this in a clean way?

It might well be that dictionaries with tuples as keys are not the proper way to handle this situation.

All suggestions welcome!
解决方案
Personally, one of the things I love about python is the tuple-dict combination. What you have here is effectively a 2d array (where x = fruit name and y = color), and I am generally a supporter of the dict of tuples for implementing 2d arrays, at least when something like numpy or a database isn't more appropriate. So in short, I think you've got a good approach.

Note that you can't use dicts as keys in a dict without doing some extra work, so that's not a very good solution. 

That said, you should also consider namedtuple(). That way you could do this:
>>> from collections import namedtuple
>>> Fruit = namedtuple("Fruit", ["name", "color"])
>>> f = Fruit(name="banana", color="red")
>>> print f
Fruit(name='banana', color='red')
>>> f.name
'banana'
>>> f.color
'red'
Now you can use your fruitcount dict:
>>> fruitcount = {Fruit("banana", "red"):5}
>>> fruitcount[f]
5
Other tricks:
>>> fruits = fruitcount.keys()
>>> fruits.sort()
>>> print fruits
[Fruit(name='apple', color='green'), 
 Fruit(name='apple', color='red'), 
 Fruit(name='banana', color='blue'), 
 Fruit(name='strawberry', color='blue')]
>>> fruits.sort(key=lambda x:x.color)
>>> print fruits
[Fruit(name='banana', color='blue'), 
 Fruit(name='strawberry', color='blue'), 
 Fruit(name='apple', color='green'), 
 Fruit(name='apple', color='red')]
Echoing chmullig, to get a list of all colors of one fruit, you would have to filter the keys, i.e. 
bananas = [fruit for fruit in fruits if fruit.name=='banana']


                        
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