[Python-ideas] Consider adding clip or clamp function to math

[Victor Stinner]

I dislike this API. What's the point of calling clamp(x)? clamp(b, a) is
min(a, b) and clamp(a, max_val=b) is just max(a, b). My point is that all
parameters must be mandatory.

Victor
Le 31 juil. 2016 6:41 AM, "David Mertz" <mertz at gnosis.cx> a écrit :

> Is there some special subtlety or edge case where a hand rolled function
> will go wrong? I like the SO version spelled like this (a little fleshed
> out):
>
> def clamp(val, min_val=None, max_val=None):
>     min_val = val if min_val is None else min_val
>     max_val = val if max_val is None else max_val
>     assert min_val <= max_val
>     return max(min(val , max_val), min_val)
>
>
> On Sat, Jul 30, 2016 at 2:57 PM, Neil Girdhar <mistersheik at gmail.com>
> wrote:
>
>> It's common to want to clip (or clamp) a number to a range.  This feature
>> is commonly needed for both floating point numbers and integers:
>>
>>
>> http://stackoverflow.com/questions/9775731/clamping-floating-numbers-in-python
>>
>> http://stackoverflow.com/questions/4092528/how-to-clamp-an-integer-to-some-range-in-python
>>
>> There are a few approaches:
>>
>> * use a couple ternary operators (e.g.
>> https://github.com/scipy/scipy/pull/5944/files  line 98, which generated
>> a lot of discussion)
>> * use a min/max construction,
>> * call sorted on a list of the three numbers and pick out the first, or
>> * use numpy.clip.
>>
>> Am I right that there is no *obvious* way to do this?  If so, I suggest
>> adding math.clip (or math.clamp) to the standard library that has the
>> meaning:
>>
>> def clip(number, lower, upper):
>>     return lower if number < lower else upper if number > upper else
>> number
>>
>> This would work for non-numeric types so long as the non-numeric types
>> support comparison.  It might also be worth adding
>>
>> assert lower < upper
>>
>> to catch some bugs.
>>
>> Best,
>>
>> Neil
>>
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>
>
>
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