I want to limit a number to be within a certain range. Currently, I am doing the following:
minN = 1
maxN = 10
n = something() #some return value from a function
n = max(minN, n)
n = min(maxN, n)
This keeps it within minN and maxN, but it doesn't look very nice. How could I do it better?
PS: FYI, I am using Python 2.6.
def clamp(n, minn, maxn):
return max(min(maxn, n), minn)
or functionally equivalent:
clamp = lambda n, minn, maxn: max(min(maxn, n), minn)
now, you use:
n = clamp(n, 7, 42)
or make it perfectly clear:
n = minn if n < minn else maxn if n > maxn else n
even clearer:
def clamp(n, minn, maxn):
if n < minn:
return minn
elif n > maxn:
return maxn
else:
return n
def clamp(n, minn, maxn): return min(max(n, minn), maxn) slightly improves readability with arguments in the same order.
np.clip()).Simply use numpy.clip() (doc):
n = np.clip(n, minN, maxN)
It also works for whole arrays:
my_array = np.clip(my_array, minN, maxN)
If you want to be cute, you can do:
n = sorted([minN, n, maxN])[1]
min(max(...)...) is about 1.4 times faster. Details: python -m timeit -s "min_n = 10; max_n = 15" "for x in range(30): max(min(x, max_n), min_n)":7.28 usec per loop. python -m timeit -s "min_n = 10; max_n = 15" "for x in range(30): sorted([min_n, x, max_n])[1]": 10.2 usec per loop. "min_n = 1000; max_n = 15000" "for x in range(-15000, 30000): ...": 11 msec per loop, "min_n = 1000; max_n = 15000" "for x in range(-15000, 30000): ...": 14.8 msec per loop
Define a class and have a method for setting the value which performs those validations.
Something vaguely like the below:
class BoundedNumber(object):
def __init__(self, value, min_=1, max_=10):
self.min_ = min_
self.max_ = max_
self.set(value)
def set(self, newValue):
self.n = max(self.min_, min(self.max_, newValue))
# usage
bounded = BoundedNumber(something())
bounded.set(someOtherThing())
bounded2 = BoundedNumber(someValue(), min_=8, max_=10)
bounded2.set(5) # bounded2.n = 8
python conditional statements?I came across this question when looking for a way to limit pixel values between 0 and 255, and didn't think that using max() and min() was very readable so wrote the following function:
def clamp(x, minn, maxx):
return x if x > minn and x < maxx else (minn if x < minn else maxx)
I would be interested to see how someone more experienced than me would find this way of clamping a value. I assume it must be less efficient than using min() and max(), but it may be useful for someone looking for a more readable (to me at least) function.
