How do I find the difference between two values without knowing which is larger?

Question

I was wondering if there was a function built into Python that can determine the distance between two rational numbers but without me telling it which number is larger. e.g.

>>>distance(6,3)
3
>>>distance(3,6)
3

Obviously I could write a simple definition to calculate which is larger and then just do a simple subtraction:

def distance(x, y):
    if x >= y:
        result = x - y
    else:
        result = y - x
    return result

but I'd rather not have to call a custom function like this. From my limited experience I've often found Python has a built in function or a module that does exactly what you want and quicker than your code does it. Hopefully someone can tell me there is a built in function that can do this.

Answer 1

abs(x-y) will do exactly what you're looking for:

In [1]: abs(1-2)
Out[1]: 1

In [2]: abs(2-1)
Out[2]: 1

Answer 2

Although abs(x - y) and equivalently abs(y - x) work, the following one-liners also work:

• math.dist((x,), (y,)) (available in Python ≥3.8)

• math.fabs(x - y)

• max(x - y, y - x)

• -min(x - y, y - x)

• max(x, y) - min(x, y)

• (x - y) * math.copysign(1, x - y), or equivalently (d := x - y) * math.copysign(1, d) in Python ≥3.8

• functools.reduce(operator.sub, sorted([x, y], reverse=True))

All of these return the euclidean distance(x, y).

Answer 3

If you have an array, you can also use numpy.diff:

import numpy as np
a = [1,5,6,8]
np.diff(a)
Out: array([4, 1, 2])