字典的键可以是一个范围吗？

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This topic created in 2982 days ago, the information mentioned may be changed or developed.

想做一个判断十六个风向的函数，输入角度，输出风向的字符串。感觉写十六个 if else 很不好，这个可以用字典做吗？或是其他什么方法？

字典

风向

else

字符

14 replies • 2018-04-09 19:40:21 +08:00

am241

Apr 9, 2018 via Android

用除法

ecnelises

Apr 9, 2018

如果这些范围都互相不重合的的话，你可以自己设计一个散列函数

orangeD

Apr 9, 2018

Guava 的 RangeMap 了解一下
http://www.baeldung.com/guava-rangemap

araraloren

Apr 9, 2018

refer this: https://stackoverflow.com/questions/4901815/object-of-custom-type-as-dictionary-key

chairuosen

Apr 9, 2018

选范围中间值作为离散点，然后输入数据除以单位角度后四舍五入就行。

zhengxiaowai

Apr 9, 2018

看看我的《 Python 如何传递运算表达式》

https://hexiangyu.me/2018/04/02/pass-operation-expression/

然后你就可以优雅的消除掉无脑 if-else 的写法

```
>>> exp = Expression()
>>> data = [1, 3, 4, 5, 6, 8, 9]
>>> pick_range(data, 1 < exp, exp < 6)
[3, 4, 5]
>>> pick_range(data, 1 <= exp, exp < 6)
[1, 3, 4, 5]
>>> pick_range(data, 1 < exp, exp <= 6)
[3, 4, 5, 6]
>>> pick_range(data, 1 <= exp, exp <= 6)
[1, 3, 4, 5, 6]
>>>
```

xomix

Apr 9, 2018

你这个做个 Enum 枚举不是更好吗…………

lain0

Apr 9, 2018

可以類似這樣子嗎？

horz, vert = cos(angle), sin(angle)

horz_desc = ''
if abs(horz) > some_threshold:
horz_desc = 'east' if horz > 0 else 'west'

vert_desc = ''
if abs(vert) > some_threshold:
vert_desc = 'north' if vert > 0 else 'south'

return ' '.join([vert_desc, horz_desc])

RuiQ

Apr 9, 2018

In [18]: from bisect import bisect

In [19]: def windy(angle, base=[0,90,180,270,360], name="/北风 /东风 /南风 /西风"):
...: i = bisect(base, angle)
...: return name.split('/')[i]
...:

In [20]: windy(0)
Out[20]: '北风'

In [21]: windy(90)
Out[21]: '东风'

In [22]: windy(15)
Out[22]: '北风'

In [23]: windy(100)
Out[23]: '东风'

In [24]: windy(200)
Out[24]: '南风'

In [25]: windy(280)
Out[25]: '西风'