Specify a range (upper and lower bound) for a variable in Python

Question

Is there a way to specify bounds for a float variable in Python? For example, when I import data, I would like to either check if it within certain range such that min <= variable <=max . Further, if possible, I would like assign a specific value to such variable if the imported value is outside of these bounds (or even missing).

I can perhaps do the first part if the variable was a float.

def var_check(x,lower_bound=3,upper_bound=30):
    rng = range(lower_bound,upper_bound+1)
    if x not in rng:
        return (upper_bound-lower_bound)/2
    else:
        return x

x = var_check(5) returns 5, while x = var_check(50) returns 13.

Any ideas on how to do this for a float variable?

Answer 1

You can do almost exactly what you wrote in your question:

def var_check(x, lower_bound=3, upper_bound=30):
    if lower_bound <= x <= upper_bound:
        return x
    else:
        return (upper_bound - lower_bound) / 2

You should do the same with integers, by the way, at least in Python 2. In Python 3 (or with xrange in Python 2), it doesn't matter so much.

Answer 2

A solution could look like this:

def var_check(x, lower_bound=3, upper_bound=30):
    if x >= lower_bound and x <= upper_bound:
        return x
    return (upper_bound-lower_bound)/2

print(var_check(2.5))
print(var_check(15.5))
print(var_check(33.5))

Output

13.5
15.5
13.5

Answer 3

You can define a class and override its __float__

class MyFloat:
   def __init__(self, num, upper=20, lower=10):
       self.num = num
       self.upper = upper
       self.lower = lower

   def __float__(self):
       if self.lower <= self.num <= self.upper:
           return float(self.num)
       else:
           return (self.upper - self.lower) / 2

Then while importing your data you can do

>>> data = [1,2,3,10,11,12,21,22,23]
>>> [float(MyFloat(d)) for d in data]
>>> [5.0, 5.0, 5.0, 10.0, 11.0, 12.0, 5.0, 5.0, 5.0]