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

[Victor Stinner]

When I really need such function, I define it like this:

def clamp(min_val, value, max_val): return min(max(min_val, value), max_val)

Test: min_val <= result <= max_val.

The parameter order is chosen to get something looking like min_val <=
value (result in fact) <= max_val.

If you need special handling of NaN, I suggest to add a special version in
the math module.

I'm not sure that it's worth it to add such new function to the standard
library.

Victor

Le 31 juil. 2016 6:13 AM, "Neil Girdhar" <mistersheik at gmail.com> a écrit :

> 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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