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

David Mertz mertz at gnosis.cx
Sun Jul 31 00:41:07 EDT 2016

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

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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