范围作为 Python 中的字典键 [英] Range as dictionary key in Python

问题描述

所以，我有一个想法，我可以使用一系列数字作为字典中单个值的键.

So, I had an idea that I could use a range of numbers as a key for a single value in a dictionary.

我写了下面的代码，但我无法让它工作.甚至有可能吗?

I wrote the code bellow, but I cannot get it to work. Is it even possible?

    stealth_roll = randint(1, 20)
    # select from a dictionary of 4 responses using one of four ranges.
    ## not working.
    stealth_check = {
                    range(1, 6) : 'You are about as stealthy as thunderstorm.',
                    range(6, 11) : 'You tip-toe through the crowd of walkers, while loudly calling them names.',
                    range(11, 16) : 'You are quiet, and deliberate, but still you smell.',
                    range(16, 20) : 'You move like a ninja, but attracting a handful of walkers was inevitable.'
                    }

    print stealth_check[stealth_roll]

推荐答案

这在 Python 3 上是可能的——如果您使用 xrange 而不是 range，则在 Python 2 上是可能的:

It is possible on Python 3 — and on Python 2 if you use xrange instead of range:

stealth_check = {
                xrange(1, 6) : 'You are about as stealthy as thunderstorm.', #...
                }

但是，您尝试使用它的方式是行不通的.您可以遍历键，如下所示:

However, the way you're trying to use it it won't work. You could iterate over the keys, like this:

for key in stealth_check:
    if stealth_roll in key:
        print stealth_check[key]
        break

这个的性能不好 (O(n)) 但如果它是一个像你展示的那样的小字典，那就没问题了.如果您真的想这样做，我会将 dict 子类化为自动工作:

Performance of this isn't nice (O(n)) but if it's a small dictionary like you showed it's okay. If you actually want to do that, I'd subclass dict to work like that automatically:

class RangeDict(dict):
    def __getitem__(self, item):
        if not isinstance(item, range): # or xrange in Python 2
            for key in self:
                if item in key:
                    return self[key]
            raise KeyError(item)
        else:
            return super().__getitem__(item) # or super(RangeDict, self) for Python 2

stealth_check = RangeDict({range(1,6): 'thunderstorm', range(6,11): 'tip-toe'})
stealth_roll = 8
print(stealth_check[stealth_roll]) # prints 'tip-toe'

这篇关于范围作为 Python 中的字典键的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！