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@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/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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